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Expanding the Ambient-Pressure Phase Space of CaFe2O4-Type Sodium Postspinel Host–Guest Compounds
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  • Justin C. Hancock
    Justin C. Hancock
    Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
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    Orcidhttps://orcid.org/0000-0002-3610-291X
  • Kent J. Griffith
    Kent J. Griffith
    Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
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    Orcidhttps://orcid.org/0000-0002-8096-906X
  • Yunyeong Choi
    Yunyeong Choi
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
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  • Christopher J. Bartel
    Christopher J. Bartel
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
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    Orcidhttps://orcid.org/0000-0002-5198-5036
  • Saul H. Lapidus
    Saul H. Lapidus
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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    Orcidhttps://orcid.org/0000-0002-7486-4325
  • John T. Vaughey
    John T. Vaughey
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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    Orcidhttps://orcid.org/0000-0002-2556-6129
  • Gerbrand Ceder
    Gerbrand Ceder
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
    Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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    Orcidhttps://orcid.org/0000-0001-9275-3605
  • Kenneth R. Poeppelmeier*
    Kenneth R. Poeppelmeier
    Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
    Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States
    *Email: [email protected]
    More by Kenneth R. Poeppelmeier
    Orcidhttps://orcid.org/0000-0003-1655-9127
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ACS Organic & Inorganic Au

Cite this: ACS Org. Inorg. Au 2022, 2, 1, 8–22
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https://doi.org/10.1021/acsorginorgau.1c00019
Published September 1, 2021

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Abstract

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CaFe2O4-type sodium postspinels (Na-CFs), with Na+ occupying tunnel sites, are of interest as prospective battery electrodes. While many compounds of this structure type require high-pressure synthesis, several compounds are known to form at ambient pressure. Here we report a large expansion of the known Na-CF phase space at ambient pressure, having successfully synthesized NaCrTiO4, NaRhTiO4, NaCrSnO4, NaInSnO4, NaMg0.5Ti1.5O4, NaFe0.5Ti1.5O4, NaMg0.5Sn1.5O4, NaMn0.5Sn1.5O4, NaFe0.5Sn1.5O4, NaCo0.5Sn1.5O4, NaNi0.5Sn1.5O4, NaCu0.5Sn1.5O4, NaZn0.5Sn1.5O4, NaCd0.5Sn1.5O4, NaSc1.5Sb0.5O4, Na1.16In1.18Sb0.66O4, and several solid solutions. In contrast to earlier reports, even cations that are strongly Jahn–Teller active (e.g., Mn3+ and Cu2+) can form Na-CFs at ambient pressure when combined with Sn4+ rather than with the smaller Ti4+. Order and disorder are probed at the average and local length-scales with synchrotron powder X-ray diffraction and solid-state NMR spectroscopy. Strong ordering of framework cations between the two framework sites is not observed, except in the case of Na1.16In1.18Sb0.66O4. This compound is the first example of an Na-CF that contains Na+ in both the tunnel and framework sites, reminiscent of Li-rich spinels. Trends in the thermodynamic stability of the new compounds are explained on the basis of crystal-chemistry and density functional theory (DFT). Further DFT calculations examine the relative stability of the CF versus spinel structures at various degrees of sodium extraction in the context of electrochemical battery reactions.

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Introduction

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The CaFe2O4 (calcium ferrite or CF) structure, also occasionally referred to as the CaV2O4 structure because it was identified first for this compound, (1,2) has been of increasing interest in recent years. Previously, the structure type was primarily of geological and crystal-chemical relevance. (3−8) Many spinel compounds transform to this structure type under high pressure (hence the CF structure is termed “post-spinel”), and the structure is thought be a host for various cations in the Earth’s mantle. (3−10) However, many property- and application-oriented studies have been recently published, indicating renewed interest in this class of materials. (11−28) Materials that crystallize in the CF structure (see Figure 1) have been reported with interesting magnetic and electronic properties resulting from its pseudo-1D chain structure and geometric frustration. (11−15) The large tunnels in CF compounds have led to their investigation as host structures for phosphors (16−18) and battery cathode materials. (19−28) CF host structures have been shown to function well as both Na and Li cathode materials, (19,20,23,24) and Mg ions are also predicted to be mobile in the tunnels. (26,27)

Figure 1

Figure 1. CaFe2O4 structure. Gray spheres represent Na+. Green and blue octahedra represent the two symmetrically independent framework sites comprising the two “double rutile” chains.

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The calcium ferrite (CF) structure is composed of a framework of octahedrally coordinated cations, arranged into “double-rutile” chains that run parallel to the b axis. Within the chains, the octahedra are edge-sharing, and the chains connect to adjacent chains via corner-sharing. There are two crystallographically distinct metal sites in the framework, with each double chain containing only one unique site, paired by symmetry, as illustrated in Figure 1. The chains surround one-dimensional channels of 8-coordinate cations. For the CF materials synthesizable at ambient pressure, the tunnel sites have been reported to be occupied by Na+, Ca2+, Sr2+, and Ba2+. (29) CF compounds with Na+ occupying the tunnel sites (compounds hereafter referred to as Na-CFs) are the most likely to be relevant to the energy storage materials community because of the relatively high mobility of Na+. Divalent Ca2+ is expected to show low mobility, (28) and Sr2+ and Ba2+ primarily form CF structures when the framework cations are redox inactive trivalent rare-earth metals. (29) However, Na-CF materials with redox-active transition metal cations have been synthesized at ambient pressure, although the library of such compounds, detailed in the following paragraph, is limited.
The only comprehensive study of the crystal chemistry of Na-CF phases was performed by Reid, Wadsley, and Sienko, who studied compounds of the formula NaA3+B4+O4 using high-temperature solid-state synthesis. (8) They synthesized and evaluated NaScTiO4, NaFeTiO4, NaFeSnO4, NaScZrO4, NaScHfO4, and NaAlGeO4, the last of which required high pressure. Other compositions, such as NaMnTiO4, were attempted but resulted in no CF phases. Based on these results, Reid et al. concluded that “spherical” (Jahn–Teller inactive) ions favor formation of a CF phase. Several new compounds of this type have since been reported, (25,30−32) although many require high pressure for synthesis, such as NaAlSiO4, NaV2O4, NaCr2O4, NaMn2O4, and NaRh2O4. (5,6,11,12,33,34) Na-CF compounds with other stoichiometries have also been shown to exist, including NaA2+0.5B4+1.5O4 (A2+ = Co2+, Ni2+ and B4+ = Ti4+) and NaA3+1.5B5+0.5O4 (A3+ = Fe3+ and B5+ = Sb5+), all of which have been synthesized at ambient pressure. (35−37) The few Na-CFs deviating significantly from these stoichiometries were synthesized via hydrothermal synthesis, including Na0.55Fe0.28Ti1.72O4 and Na3Mn4Te2O12 (Na[Mn1.33Te0.67]O4), the latter having a superstructure owing to crystallographic ordering of Te6+ and Mn2+/3+. (38,39) Notably, some of the CF phases synthesized at ambient pressure contain ions that are weakly Jahn–Teller active, thus the spherical ion preference appears not to be a strict criterion. This would suggest many more as yet undiscovered Na-CF compounds may be stable even at ambient pressure.
In this paper, we report a large expansion of the ambient-pressure phase space of Na-CF materials and critically examine the crystal chemical relationships. Notably, we successfully synthesized several new Na-CFs with redox-active transitions metals, which are prospective Na/Li/Mg battery electrode materials, and Na1.16In1.18Sb0.66O4, the first Na-CF that contains sodium on both the tunnel and framework sites.

Experimental Section

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Synthesis

All compounds were synthesized via high-temperature solid-state reactions. The synthesis temperature depended on the composition of the CF phase. Unless stated otherwise, starting materials were NaHCO3 and binary metal oxides. In a typical synthesis, appropriate amounts of these reactants were mixed with a mortar and pestle then pressed into a pellet at 400 MPa. The pellet was placed in either a platinum crucible (air syntheses) or platinum boat (inert atmosphere syntheses), heated at the specified temperature for 2 days, ground into a powder, and repeated as necessary. Some compositions (those containing Cr3+, Mn2+, and Fe2+) required an inert atmosphere for synthesis. These samples were heated in a tube furnace under flowing argon, with a titanium rod placed upstream to remove any residual O2. In some cases, excess NaHCO3 was added in the subsequent annealing steps to account for sodium loss from volatilization. All reactions carried out in air (except NaMnSnO4, for which we were reproducing a reported synthesis) were quenched on the benchtop to reflect the thermodynamics of the synthesis temperature and minimize cooling rate effects. All reactions carried out in a tube furnace were cooled by shutting off the power once the dwell step completed. Detailed synthetic information for each new compound is discussed in more detail in the Results and Discussion section, and reaction conditions for combinations of cations that did not produce a CF phase are included in Table S1.

X-ray Diffraction

Phase purity was assessed by laboratory powder X-ray diffraction (PXRD) using both Rigaku Ultima IV and Rigaku SmartLab X-ray diffractometers. These data were collected over a 2θ range of 10–60° under ambient conditions. Synchrotron X-ray radiation was used for Rietveld refinements, except in the case of NaFe0.5Ti1.5O4, NaMn0.5Sn1.5O4, NaFe0.5Sn1.5O4, and NaCd0.5Sn1.5O4. These data were collected at 11-BM at the Advanced Photon Source at Argonne National Laboratory using a wavelength of 0.45788 Å (∼27 keV). This wavelength was chosen to minimize absorption of X-rays by In and Sn. Samples were packed into Kapton capillaries.
Rietveld refinement was performed using the General Structure Analysis System II (GSAS II) package. (40) Ionic scattering factors were used in all cases. All data were refined against an orthorhombic unit cell (space group Pnma). In all cases, the unit cell parameters, atomic coordinates, and Uiso values were refined. In the case of NaCd0.5Sn1.5O4 only, Uiso for the oxygen atoms was not refined and set to a reasonable value of 0.01. An 8- or 10-term Chebyshev polynomial was used to fit the backgrounds, with an added background peak to account for scattering from the Kapton capillary. To decrease the degrees of freedom, global compositions were fixed, and atomic positions and isotropic thermal parameters were constrained to be equal for all atoms sharing the same crystallographic sites. In cases where cation ordering of the framework sites seemed probable (see the Results and Discussion section), occupancies were refined, but in most cases occupation of the framework sites was assumed to be statistically distributed to simplify the model and avoid overfitting.

Solid-State NMR Spectroscopy

23Na solid-state NMR spectra were recorded at 9.4 T (νL(23Na) = 105.7 MHz) with a Bruker Avance III spectrometer and a Bruker HX probe. Samples were packed into a 4.0 mm diameter (80 μL volume) zirconia rotor with a Kel-F cap and measured at ambient temperature under 12.5 kHz magic-angle spinning (MAS), corresponding to approximately 30 °C, unless otherwise noted. One-dimensional spectra were collected with a one-pulse (Bloch decay) sequence and a 2.0 μs (π/4)liquid pulse. NaCl (aqueous, 1.0 M) was used to optimize the solution π/2 pulse and as the 23Na reference at 0 ppm. In all cases, the recycle delay was set to at least 5 × T1, where T1 is measured with a saturation-recovery pulse sequence. Typical T1 relaxation times were 0.5–8 s. The multiple-quantum magic-angle spinning (MQMAS) spectrum of Na1.16In1.18Sb0.66O4 was recorded with a z-filtered pulse sequence with excitation and conversion pulses of 9.0 and 3.0 μs followed by a 28 μs selective pulse. (41) Acquisition in the indirect dimension comprised 192 t1 increments of 25 μs. For each t1-slice, 396 scans were averaged and the recycle delay was 0.6 s, resulting in an experimental time of 12.7 h.

DFT Calculations

Calculations is this work are based on density functional theory (DFT) as implemented in the Vienna Ab Initio Simulation Package (VASP) (42) using the projector augmented-wave method (43,44) and the generalized gradient approximation as formulated by Perdew, Burke, and Ernzerhof. (45) For all calculations, the energy cutoff was set to 520 eV, and at least 1000 k-points were used per reciprocal atom. For geometry optimizations, energies were converged to 10–5 eV for electronic steps and 10–4 eV for ionic steps. The Hubbard U correction was used for the transition metal atoms to account for the self-interaction error of semilocal density functionals. (46) U parameters were chosen to be consistent with the Materials Project database, (47) as reported by Jain et al. (Co, 3.32 eV; Cr, 3.7 eV; Fe, 5.3 eV; Mn, 3.9 eV; Ni, 6.2 eV). (48)
Supercells of the spinel (Fd3̅m) and CF postspinels (Pnma) with 32 oxygen ions (Nax(A,B)16O32) were used for all calculations, and the ionic positions, cell shape, and volume were allowed to optimize during relaxations. The cell size was chosen to provide enough ions for sampling various occupations for Na and Na vacancies on the alkali site as well as A and B on the octahedral sies. To generate ordered structures, the lowest and second lowest electrostatic energy configurations (as calculated with the Ewald method) were sampled to order the A and B cations on the octahedral sites and determine which Na sites to remove. In most compositions, two different configurations were used but in slow converging composition only the lowest configuration was used for DFT calculation. In total, 264 different structures were calculated at varying levels of sodiation (x) to determine the thermodynamic stability of each phase in the spinel and postspinel structures. Thermodynamic stability was determined using the convex hull method, where the formation energies of all competing phases in each Na-A-B-O chemical space were taken from the Materials Project database. The pymatgen library was used to set up and analyze the calculations in this work. (49)

Results and Discussion

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The Na-CF chemical space was systematically explored using numerous cation combinations and stoichiometries, and this approach and the results are summarized schematically in Figure 2. Sixteen new Na-CF end-member compounds were successfully synthesized, and NaMnSnO4, reported recently by Chiring et al., (25) was reexamined. Rietveld refinement data for these compounds are shown in Table 1, and an example Rietveld refinement is shown in Figure 3. Additional Rietveld refinements are shown in Figures S1–S16.

Figure 2

Figure 2. Schematic summarizing the synthetic approach and results presented in this paper. The ion combinations in green were successfully synthesized in the postspinel structure, whereas the ion combinations in red formed alternative phases.

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Table 1. Rietveld Refinement Data for New Na-CF Compounds
sourcesynchrotron
chemical formulaNa0.99Cr0.99Ti1.01O4Na0.96Rh0.96Ti1.04O4NaCrSnO4NaMnSnO4Na0.96In0.96Sn1.04O4NaMg0.5Ti1.5O4
formula weight186.61234.67257.67260.61319.73170.99
temperature (K)298
wavelength (Å)0.457880
crystal systemorthorhombic
space group (no.)Pnma (62)
a (Å)9.101854(15)9.16953(5)9.26744(3)9.42779(10)9.53203(3)9.17179(2)
b (Å)2.933813(4)2.947138(15)3.048247(9)3.02517(3)3.172342(8)2.968472(6)
c (Å)10.668108(17)10.79754(5)10.93396(4)11.11389(11)11.29355(3)10.76171(2)
α = β = γ (deg)90
V (Å3)284.872(1)291.791(3)308.878(2)316.976(7)341.504(2)290.001(1)
Z4
profile range3 ≤ 2θ ≤ 37.9963
GOF1.931.042.032.382.461.40
Rp (%)6.8210.607.719.926.556.27
Rwp (%)9.7012.889.7212.449.107.37
sourcesynchrotron
chemical formulaNaMg0.5Sn1.5O4NaCo0.5Sn1.5O4NaNi0.5Sn1.5O4NaCu0.5Sn1.5O4NaZn0.5Sn1.5O4NaSc1.5Sb0.5O4
formula weight277.17294.49294.37296.79297.71215.3
temperature (K)298
wavelength (Å)0.457880
crystal systemorthorhombic
space group (no.)Pnma (62)
a (Å)9.41987(3)9.41576(3)9.39739(3)9.47695(3)9.43720(5)9.44848(6)
b (Å)3.106399(8)3.115976(8)3.099946(7)3.101415(7)3.113964(15)3.133693(18)
c (Å)11.11941(3)11.10660(3)11.10428(3)11.08428(3)11.13601(6)11.13570(7)
α = β = γ (deg)90
V (Å3)325.375(2)325.859(2)323.483(2)325.789(2)327.255(4)329.713(4)
Z4
profile range3 ≤ 2θ ≤ 37.9963
GOF1.341.851.542.011.662.08
Rp (%)7.486.316.966.488.799.83
Rwp (%)8.968.339.108.2612.4512.40
sourcesynchrotronCu Kα
chemical formulaNa1.16In1.18Sb0.66O4NaFe0.5Ti1.5O4NaMn0.5Sn1.5O4NaFe0.5Sn1.5O4NaCd0.5Sn1.5O4
formula weight306.51186.76292.49292.94321.23
temperature (K)298298
wavelength (Å)0.4578801.5406
crystal systemorthorhombicorthorhombic
space group (no.)Pnma (62)Pnma (62)
a (Å)9.53383(2)9.2175(3)9.48122(13)9.40435(15)9.5604(2)
b (Å)3.168104(6)2.96553(9)3.13771(4)3.11440(5)3.17096(7)
c (Å)11.28573(2)10.7674(4)11.19800(15)11.10497(18)11.2812(3)
α = β = γ (deg)9090
V (Å3)340.876(1)294.33(2)333.133(9)325.252(11)341.995(17)
Z44
profile range3 ≤ 2θ ≤ 37.996310 ≤ 2θ ≤ 13010 ≤ 2θ ≤ 120
GOF2.161.812.262.422.55
Rp (%)8.651.843.342.833.99
Rwp (%)11.612.554.453.965.36

Figure 3

Figure 3. Rietveld refinement using synchrotron data for NaMg0.5Ti1.5O4. Blue crosses are the observed intensities, the green curve is the fitted pattern, the black curve is the difference pattern, and the red tick marks indicate the location of the CF-NaMg0.5Ti1.5O4 peaks.

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Synthetic Studies

New Postspinels in the Na+-A3+-B4+-O2– System (Idealized Formula: NaA3+B4+O4)

The new CF phase NaCrTiO4 was successfully synthesized at ambient pressure. NaCrTiO4 must be synthesized in an inert atmosphere (Ar in this case) to avoid the oxidation of Cr3+ to Cr6+ and formation of Na2CrO4. Initially, reactions performed in the temperature range of 875–900 °C were used to minimize sodium volatility. For a 1:1:1 Na/Cr/Ti ratio, after 48 h a mixture of three quaternary phases formed, which included a CF phase, layered Na1–xCr1–xTixO2, probably close to the Na0.6Cr0.6Ti0.4O2 composition reported by Avdeev et al., (50) and NaxCrxTi2–xO4, with a nonstoichiometric sodium iron titanate (NSIT) structure. The NSIT phase probably has a composition close to Na0.9Cr0.9Ti1.1O4, which is the reported upper limit of x found in the NaxFexTi2–xO4 system. (51) (Note that, confusingly, NSIT phases are sometimes referred to as CaV2O4-type structures in databases, but we emphasize that the NSIT structure is distinct from the CF structure.) While the quaternary phases formed relatively quickly, they reacted very slowly with each other, and the system was slow to reach thermal equilibrium once these phases formed. Heating the mixture for an additional 48 h at 900 °C increased the percentage of CF-NaCrTiO4, but the other two phases were still present. Higher temperatures sped up the reaction, and the loss of Na from volatility appears to be minimal at 950 °C. At this temperature, the NSIT phase was no longer observed. Instead, the stoichiometric mixture (1:1:1 Na/Cr/Ti) resulted in Na0.6Cr0.6Ti0.4O2 and the CF compound (see Figure 4), the relative ratios of which changed little upon further heating. This suggests that the CF compound is nonstoichiometric and is deficient in both sodium and chromium relative to the ideal composition NaCrTiO4. Addition of ∼2% excess TiO2 to this mixture and further annealing at 900 °C led to a nearly single-phase product, suggesting an actual composition of Na0.99Cr0.99Ti1.01O4 for the CF phase. A separate mixture synthesized at 950 °C with 5% TiO2 excess still contained some Na0.6Cr0.6Ti0.4O2, suggesting the composition of the CF phase may have some degree of temperature dependency. Because the competing phases have such similar stoichiometries, the ratio of cations must be carefully controlled to avoid significant fractions of the non-CF phases.

Figure 4

Figure 4. Powder XRD patterns for the 1:1:1 and 0.99:0.99:1.01 Na/Cr/Ti samples compared to a calculated pattern for the CF phase. Asterisks highlight peaks from the secondary phase Na0.6Cr0.6Ti0.4O2 in the 1:1:1 Na/Cr/Ti sample.

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The synthesis of NaCrSnO4 requires higher temperatures than that of NaCrTiO4. The formation of the CF phase was slow even at 950 °C, and NaCrO2 and SnO2 were the main phases after 48 h. Heating at 1000 °C produced CF-NaCrSnO4 as the main phase, but NaCrO2, potentially Sn-substituted, also formed, and SnO2 was still present at shorter reaction times. Reheating these mixtures again at 1000 °C resulted in elimination of the SnO2 phase, but with similar proportions of NaCrO2 and CF-NaCrSnO4. This suggests a loss of Sn. In some runs, metallic Sn was observed. Cleaning the alumina tube alleviated this problem somewhat, suggesting reductive species build up over time in the tube, potentially from the Ti rod, used as a getter, and its interaction with volatile phases. Nevertheless, phase-pure NaCrSnO4 was never obtained by this synthetic method alone, even when using excess SnO2, but the pure CF phase could likely be formed in a closed system such as a sealed metal tube. However, purification was possible. NaCrO2 was removed by treating the mixture with molten KNO3, which selectively oxidized the NaCrO2. The soluble Cr(VI) products were then dissolved in water, and the remaining solid was filtered, leaving behind only CF-NaCrSnO4.
Recently, CF-NaMnSnO4 was reported to be synthesizable under ambient pressure in air. (25) The authors reported that, when using a stoichiometric starting composition, phase purity was achieved only by slowly cooling at 0.5 °C/min after heating at 1200 °C for a day. Similarly, we observed secondary phases upon quenching stoichiometric mixtures but obtained a nearly phase-pure CF compound upon quenching a sample with a Na/Mn/Sn ratio of 0.96:0.96:1.04. The lattice parameters for the quenched and slowly cooled samples are significantly different, suggesting the difference in composition is real. These results, like those for the Na–Cr–Ti–O system, suggest a temperature dependence of the composition of the CF phase. Interestingly, both the quenched and slowly cooled samples had broad peaks with poorer Rietveld fits compared to the other compositions, probably caused by a high degree of strain. Presumably, this strain results from substituting a strongly JT-active cation (Mn3+) that prefers highly distorted octahedral environments into sites that usually contain more spherically symmetric cations.
CF-NaRhTiO4 was synthesized in air from NaRhO2 (prepared by heating NaHCO3 and metallic Rh powder at 900 °C for about 1 day) and TiO2. A layered phase similar to the one formed in the Na–Cr–Ti-O system, NaxRh1–xTixO2 forms quickly, with subsequent slow formation of the CF phase at 900 °C. Increasing the temperature to 950 °C increases the rate of formation, and the CF phase is the major phase after 48 h. However, heating at 1050 °C destabilizes the CF phase. At this temperature, no CF phase is observed, and the layered phase is the primary phase along with another unknown phase present in small amounts. As in the case of Na1–xCr1–xTi1+xO4, phase purity was not achieved with the ideal stoichiometry. In fact, the product of the mixture with a 1:1:1 ratio of cations had a nearly identical PXRD pattern to that of the 1:1:1 ratio in the Na–Cr–Ti–O system. Phase purity was achieved by using an excess of titanium relative to the ideal composition, and the phase-pure sample had a nominal composition of Na0.96Rh0.96Ti1.04O4. CF-NaRhSnO4 did not form under similar conditions up to a temperature of 1100 °C.
CF-NaInSnO4 appears to be more refractory than the CF phases containing Ti4+ and could be synthesized in the 950–1200 °C temperature range. The sample with the highest phase purity was synthesized by using a Na/In/Sn ratio of 0.98:0.96:1.04 and air-quenching from 1200 °C, the highest temperature studied, after ∼20 h. Thus, the actual composition of the CF phase is likely close to Na0.96In0.96Sn1.04O4, and presumably, the excess Na was lost through volatilization. Thus, all the new CF compounds of the type NaA3+B4+O4 deviate slightly from the ideal stoichiometry, with the possible exception of NaCrSnO4, whose precise composition was not determined owing to the difficulty in obtaining a phase-pure sample. CF-NaInZrO4 did not form under similar conditions.

New Postspinels in the Na+-A2+-B4+-O2– System (Idealized Formula: NaA2+0.5B4+1.5O4)

The compounds NaMg0.5Ti1.5O4 and NaFe0.5Ti1.5O4 can be synthesized with high phase purity. A stoichiometric mixture of NaHCO3, MgO, and TiO2 heated at 925 °C for 48 h resulted in primarily Na0.9Mg0.45Ti1.55O4 (NSIT-type structure). Phase-pure NaMg0.5Ti1.5O4 was not obtained until the mixture was further heated at 950 °C for ∼96 h with an intermediate grinding step. The CF phase decomposes after 3 h at 1050 °C into NSIT-Na0.9Mg0.45Ti1.55O4, layered Na0.68Mg0.34Ti0.66O2, and MgO. The presence of MgO suggests Na volatilization at this temperature. Interestingly, NaMg0.5Ti1.5O4 was not reported in a previous study of the Na–Mg–Ti–O system that found six phases, possibly because of the fast formation of the NSIT and layered phase and limited temperature range in which the CF phase can be formed. (52) NaFe0.5Ti1.5O4 was readily synthesized in one step at 925 °C with a 5% excess of sodium from Na8Ti5O14, FeTiO3, and TiO2 under flowing argon. The relatively fast kinetics of this synthesis could be explained by the use of different reactants. This phase seems somewhat air-sensitive even at room temperature. The sample used for synchrotron diffraction had highly asymmetric peaks skewed toward higher angles after being stored for ∼3 months, suggesting topotactic oxidation (Fe2+ to Fe3+). With this observation, a new sample was synthesized and laboratory X-ray data were collected for Rietveld refinement. It should be pointed out that a CF phase containing Fe2+ has been reported to form via hydrothermal synthesis, but the phase has a different composition (Na0.55Fe0.28Ti1.72O4) and is unusually Na-deficient. (38) In addition, a “CF-like” secondary phase was mentioned in a study of the NSIT phases NaxFe2+x/2Ti4+2–x/2O4 for higher values of x but was not discussed further. (53) No other divalent cations (Mn2+, Cu2+, or Zn2+) could be fully substituted into NaA2+0.5Ti4+1.5O4 under similar synthetic conditions.
No CF phases with the composition NaA2+0.5Sn1.5O4 have been previously reported. However, more compositions of this type could be synthesized than in the NaA2+0.5Ti1.5O4 system; Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ can all form CF compounds when combined with Sn4+. These compounds are more refractory than the corresponding compounds with Ti4+, so a wider range of temperatures (950–1200 °C) was used in the synthesis of the NaA2+0.5Sn1.5O4 compounds. The compounds NaA2+0.5Sn1.5O4 (A2+ = Mg2+, Co2+, Ni2+) were first heated at 1200 °C for 1 day with a 5% excess of sodium, then reground with an additional 5% excess of sodium (as NaHCO3) and reheated at 1000 °C for 2 days. The excess Na decreased the amount of SnO2 observed as a minor secondary phase. The compounds NaA2+0.5Sn1.5O4 (A2+ = Mn2+, Fe2+, Zn2+, Cd2+) were synthesized at 1000 °C for 48 h, and NaCu0.5Sn1.5O4 was synthesized at 950 °C for 96 h. NaMn0.5Sn1.5O4 and NaFe0.5Sn1.5O4 were synthesized under flowing argon, and Fe2+ was introduced as Fe(C2O4)·2H2O. In most cases, near phase purity was achieved, although it was difficult to eliminate SnO2 as a secondary phase (e.g., ∼1% by weight in the case of NaCo0.5Sn1.5O4). NaZn0.5Sn1.5O4 always formed along with secondary phases, though in the best sample, the ratio of the most intense CF peak of the PXRD pattern to the most intense secondary phase peak was slightly greater than 13:1.
While a very small degree of deviation from ideal stoichiometry is possible, no systematic trends were observed during synthesis of the NaA2+0.5B4+1.5O4 compounds that would suggest sodium vacancies, in contrast to the NaA3+B4+O4 compounds.

New Postspinels in the Na+-A3+-B5+-O2– System (Idealized Formula: NaA3+1.5B5+0.5O4)

CF phases were also found in the Na–In–Sb–O and Na–Sc–Sb–O systems. Attempts to synthesize materials of the ideal compositions NaIn1.5Sb0.5O4 and NaSc1.5Sb0.5O4 always resulted in a CF phase and either In2O3 or Sc2O3. Decreasing the ratio of In2O3 to the other reactants (NaHCO3 and Sb2O3) improved the phase purity, suggesting the composition of the CF phase is better represented by the formula Na1+xIn1.5–2xSb0.5+xO4. When x = 0.158, a single-phase CF material was obtained after heating at 1200 °C for 1 day, followed by quenching. Thus, In3+ appears to be cosubstituted by Sb5+ and Na+. We were not able to make the pure CF phase in the Na–Sc–Sb–O system using the same strategy. The best sample was synthesized at 1100 °C for 96 h with an intermediate grinding and with the ideal ratio of cations (i.e., 1:1.5:0.5 ratio of Na to Sc to Sb), but this sample contained Sc2O3 and another unknown phase as secondary phases. NaCr1.5Sb0.5O4 did not form at 900 or 950 °C under flowing argon and from a mixture of NaHCO3, NaSbO3, and Cr2O3.

Solid Solutions

Owing to similarities in synthesis conditions, ability to move from ideal cation locations, and nonstoichiometry, solid solutions between the systems NaA3+B4+O4 and NaA2+0.5B4+1.5O4 should exist. Several compositions were tried, including NaCo1/3Fe1/3Ti4/3O4, NaNi1/3Fe1/3Ti4/3O4, and NaNi1/3Sc1/3Ti4/3O4, which produced CF phases with no apparent secondary phases. NaCo1/3Fe1/3Ti4/3O4 and NaNi1/3Fe1/3Ti4/3O4 were synthesized at 900 °C for 96 h with intermediate grindings. NaNi1/3Sc1/3Ti4/3O4 also formed at these temperatures and was stable at 1050 °C, in contrast to the other Na-CFs containing Ti. The flexibility of these phases with respect to compositional tuning further emphasizes their potential usefulness for applications such as intercalation cathodes for energy storage. The results summarizing the now-expanded Na-CF phase space (excluding solid solutions) are shown in Figure 5.

Figure 5

Figure 5. A combinatorial representation of the Na-CF phase space. The phase-space shown covers all Na-CF compounds and combinations known to have been attempted in previous studies or this work. Conceivable but unexplored combinations (e.g., Sc3+ and Mo4+) are not depicted.

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Crystal Chemistry

Cation Distribution

The Na-CF material in the Na–In–Sb–O system was obtained phase pure with the nominal stoichiometry Na1.16In1.18Sb0.66O4 (Na1+xIn1.5–2xSb0.5+xO4, x = 0.16). This would imply a cosubstitution of Na+ and Sb5+ for In3+, which would be the first reported instance of Na+ occupying the framework sites of a CF compound. Rietveld refinements for this material provide further evidence of this new cation distribution. The CF structure contains two independent octahedral cation sites, which are referred to here to as the M1 and M2 sites. Assuming an actual composition of NaIn1.5Sb0.5O4 resulted in unreasonable (negative) thermal parameters (Uiso) for the M2 site, even when the occupancy of Na+ in the tunnel sites was refined. Refining the composition Na[Na0.16In1.18Sb0.66]O4 with complete disorder of the framework sites also resulted in a negative Uiso for the M2 site. Refining the fractional occupancies of the framework sites and constraining the composition alleviated this problem. Because three atoms distributed between two sites is an underdetermined system using only X-ray data and because In3+ and Sb5+ have nearly equal scattering factors, Sb5+ was treated as In3+ for this refinement. (Note that for the final refinement and in the CIF, Sb5+ was reintroduced such that the In/Sb ratio was the same for both sites.) By this refinement, nearly all (∼90%) of the octahedral Na+ occupies the M1 site rather than the M2 site, with a final distribution of Na[(In/Sb)0.856(2)Na0.144(2)]M1[(In/Sb)0.984(2)Na0.016(2)]M2O4. A model placing Na+ on the M2 site only and not allowing for occupancy refinement results in a significantly worse fit. The results of these refinements are summarized in Table 2. This Na-CF with Na+ occupying the framework sites is analogous to lithium-rich spinels such as Li4Mn5O12 (Li[Li1/3Mn5/3]O4) and the commercial lithium-ion battery material Li4Ti5O12 (Li[Li1/3Ti5/3]O4). (54,55)
Table 2. Refinement Statistics for Different Structural Models of Na1.16In1.18Sb0.66O4
starting cation distribution modelM1 and M2 site occupancies refined?Rwp (%)comment
Na[In0.75Sb0.25]M1[In0.75Sb0.25]M2O4no11.90negative Uiso for M2
Na[In0.59Sb0.33Na0.08]M1[In0.59Sb0.33Na0.08]M2O4no11.97negative Uiso for M2
Na[In0.92Na0.08]M1[In0.92Na0.08]M2O4yes11.61reasonable Uisos, 90% Na on M1 site
Na[In]M1[In0.84Na0.16]M2O4no13.30negative Uiso for M2
The sodium environments in Na1.16In1.18Sb0.66O4 were further investigated with 23Na solid-state magic-angle spinning (MAS) NMR spectroscopy. The 23Na NMR spectrum of Na1.16In1.18Sb0.66O4, shown in Figure 6a, contains a series of overlapping resonances at lower frequencies (−10 to +20 ppm), with an additional resonance at +34 ppm. The overlapping low-frequency resonances, which resolve into at least four signals with multiple-quantum magic-angle spinning (MQMAS) (Figure S17), likely correspond to Na in the tunnel sites. Although there is crystallographically only one tunnel site, the local environment is more complex given the multiple next-nearest neighbor possibilities. Multiple peaks for the tunnel sites are also resolved in some other CF phases (see Figure S18). The higher shift of the signal at 34 ppm is consistent with octahedral Na+, and the integration of this peak (11%) is reasonably consistent with the fraction of Na expected to occupy the octahedral sites. Another possibility that could explain the 23Na NMR spectrum is that the stoichiometry is ideal, NaIn1.5Sb0.5O4, but with Na+-In3+ antisite defects analogous to inversion in spinels. This is sensible crystal-chemically, as In3+ does occupy 8-coordinate sites in some phases. (56) If this did occur in NaIn1.5Sb0.5O4, it would also be expected to occur in NaInSnO4. However, the 23Na NMR spectrum for Na0.96In0.96Sn1.04O4, shown in Figure 6b, contains only the low-frequency signal distribution. Thus, we concluded antisite defects were unlikely to be the cause of the signal at 34 ppm for Na1.16In1.18Sb0.66O4. A third possibility is that the high frequency resonance is from an unidentified, and possibly amorphous, secondary phase. In the nominally stoichiometric NaIn1.5Sb0.5O4 sample, PXRD showed only CF and In2O3 as crystalline phases, and the 23Na NMR spectrum matched that of Na1.16In1.18Sb0.66O4. Since this sample is Na-poor, it is unlikely that the resonance at 34 ppm could come from a Na-containing secondary phase. The 23Na NMR spectra for “NaSc1.5Sb0.5O4” and “NaCd0.5Sn1.5O4” also show weak resonances at 35 ppm (Figure 6 and Figure S18), and these phases also probably contain framework sodium. While the CF phase in the Na–Sc–Sb–O system is likely also not quite stoichiometric NaSc1.5Sb0.5O4, a Rietveld refinement assuming this stoichiometry gave reasonable Uiso values when framework occupancies were refined. However, the 23Na NMR spectrum for the “NaSc1.5Sb0.5O4” sample (Figure 6c) contained a small peak at 35 ppm that integrates to ∼4.5% of the total Na. There was a secondary phase that we were unable to identify so we cannot conclusively say that this peak corresponds to framework-site Na in the CF phase, but it is likely given the parallels with the Na–In–Sb–O system. If “NaSc1.5Sb0.5O4” does deviate from the ideal stoichiometry, the difference is not as large as in Na1.16In1.18Sb0.66O4, and corefinements with neutron data may be necessary to determine the cation distribution accurately.

Figure 6

Figure 6. 23Na solid-state NMR spectra at 12.5 kHz MAS and 9.4 T: (a) Na1.16In1.18Sb0.66O4, (b) Na0.96In0.96Sn1.04O4, and (c) “NaSc1.5Sb0.5O4” central transition resonances.

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While the CF structure contains two crystallographically independent octahedral cation sites, each double-chain contains only one of these sites (see Figure 1). Reid et al. found no evidence of cation ordering in the Na-CFs they synthesized. (8) A single-crystal study of NaFeRuO4 also found no site preference for the framework cations Fe3+ and Ru4+. (31) Only two studies of hydrothermally synthesized Na-CFs have found any statistically significant site preference. (38,57) In these cases, the synthesis temperature is considerably lower than typically used for solid-state synthesis. As noted by Reid et al., the intensities of most of the X-ray reflections are insensitive to ordering. However, the (101) reflection is strongly affected by site preference and has negligible intensity in the absence of ordering and/or when the framework cations have similar scattering factors. Thus, in this study, occupancies of the framework cations were only refined when the (101) peak was apparent in the PXRD pattern to avoid overfitting.
None of the compounds reported here have strong (101) reflections present, but a weak reflection (note the small peak at ∼3.5° in Figure 3) indicating some degree of site preference is apparent for NaMg0.5Ti1.5O4, NaCu0.5Sn1.5O4, Na1.16In1.18Sb0.66O4, and NaSc1.5Sb0.5O4. That the CF phase obtained in the Na–In–Sb–O system has a (101) reflection is further evidence that it is not the initially expected NaIn1.5Sb0.5O4 (In3+ and Sb5+ are essentially indistinguishable by X-rays). One might expect that cation site preference is more likely when cation radii and charge density differences are larger or when JT-active cations like Mn3+ and Cu2+ are present, since these cations are expected to prefer different coordination environments than Ti4+ or Sn4+. Of the Na-CF compounds reported here, only NaMnSnO4 and NaCu0.5Sn1.5O4 contain cations with strong Jahn–Teller distortions. The (101) reflection is essentially nonexistent in the case of NaMnSnO4, even for the slowly cooled sample, thus there is no evidence of site preference. For NaCu0.5Sn1.5O4, refinement of the occupancies of the framework sites indicated that ∼63% of the Cu2+ occupies the M1 site, with Cu occupancies of 0.317(2) and 0.183(2) for the M1 and M2 sites, respectively. Likewise, ∼63% of the Mg2+ cations occupy the M1 site in NaMg0.5Ti1.5O4, with Mg occupancies of 0.316(1) and 0.184(1) on the M1 and M2 sites, respectively. The strongest cation preference was observed for Na1.158In1.184Sb0.658O4. In this instance, ∼88% of the octahedral Na+ cations sit on the M1 site according to the Rietveld refinement. In3+ and Sb5+ could preferentially occupy either of the sites too, but this cannot be determined by X-ray diffraction. NaSc1.5Sb0.5O4 also has a weak (101) reflection, and cation site preference is likely in this compound. However, because we do not know with certainty the amount of Na+ occupying the framework sites in this compound, it is difficult to identify the mechanism of this partitioning. Given these results, ordering of the framework cations in Na-CFs seems to be driven by differences in cationic radii and charge density rather than JT activity. It would be expected, then, that NaCd0.5Sn1.5O4 would show cation site preference. However, X-rays cannot distinguish between Cd2+ and Sn4+, thus the cation distribution could not be fully examined in the present work; a detailed NMR crystallography study of this question is ongoing. Neutron diffraction studies would also be a valuable complement to the work presented here, as X-ray data alone is insufficient for occupancy studies when the framework atoms differ little in electron count (e.g., NaCrTiO4 and NaCd0.5Sn1.5O4). Furthermore, each of the samples with cation site preference were quenched from the synthesis temperature. It is possible that annealing at lower temperature would increase the degree of site preference, as lower synthesis temperatures (hydrothermal synthesis) resulted in site preference in the Na–Fe–Ti–O CFs, (38,57) which was not observed for the NaFe0.5Ti1.5O4 compound synthesized by a solid-state reaction and presented in this paper.

Phase Space and Compositional Trends

CF-NaCr2O4, NaMn2O4, and NaRh2O4 have all been synthesized in the postspinel structure but required the use of high pressure. (12,32,33) The requirement of high pressure is likely due to a combination of factors. The compounds are mixed-valent, and the oxidation states of Cr and Rh therein are unusual; Rh4+ compounds often require high-pressure and highly oxidizing environments, while Cr4+ compounds also often require high pressure to avoid disproportionation into Cr3+ and Cr6+. Mn4+ can be formed at ambient pressures, but Mn3+ is strongly Jahn–Teller active. Thus, CF-NaMn2O4 would not be expected to be stable by the criteria suggested by Reid et al., which potentially explains the necessity of high pressure. Ionic radius also appears to play a role, and it should also be noted that no Na-CF synthesized under ambient pressure contains framework cations smaller than 0.60 Å (the size of Sb5+) (58) as major components. Rh4+ (0.60 Å) is similar in size to Sb5+, but both Cr4+ (0.55 Å) and Mn4+ (0.53 Å) are smaller. However, Cr3+ (0.615 Å) and Rh3+ (0.665 Å) are JT-inactive (spherical), stable, and have ionic radii consistent with cations known to form CF compounds at ambient pressure. Thus, we reasoned that replacement of Cr4+ and Rh4+ with a more stable and larger tetravalent cation like Ti4+ (0.605 Å) or Sn4+ (0.69 Å) should increase the chance of synthesizing a CF compound at ambient pressure. This strategy was successful in the synthesis of NaV3+(V0.25Ti0.75)4+O4 and NaVSnO4. (31) Indeed, it was found that Cr3+ can form a Na-CF phase when paired with either Ti4+ or Sn4+. Rh3+ formed a Na-CF phase when combined with Ti4+, though we were unable to make CF-NaRhSnO4. Reid et al. found that CF-NaMnTiO4 did not form at ambient pressure, and this result was among the evidence that the CF structure tends to form with spherical ions. Instead, a mixture corresponding to the stoichiometry NaMnTiO4 forms Na4Mn4Ti5O18 at ambient pressure. (59) This structure contains two types of tunnels: a smaller tunnel with a shape reminiscent of those found in the CF structure, and a larger S-shaped tunnel. Half of the Mn3+ cations are 5-coordinate in this structure. Likewise, “NaMn2O4” forms the isostructural Na4Mn9O18 at ambient pressure. (60) Interestingly, replacing Ti4+ with Sn4+ results in CF-NaMnSnO4.
No Na-CF compound containing In3+ has previously been reported. Reid et al. attempted to synthesize NaInTiO4 but obtained a mixture of In2O3 and Na2Ti3O7. (8) Synthesis of NaInZrO4 was attempted in this work because NaScZrO4 was reported and the size mismatch would be decreased, but that did not form either. However, NaInSnO4 was successfully synthesized. It should be noted that the ionic radius of In3+ (0.800 Å) is larger than Sc3+ (0.745 Å), which means In3+ is the largest trivalent cation known to form a Na-CF compound at ambient pressure. Y3+ (0.900 Å) is apparently too large. The compound NaYTiO4 has a layered perovskite structure instead of the CF structure. (61) In the yttrium system, replacing Ti4+ with Sn4+ or Zr4+ still did not produce a CF phase.
Only two compounds of the type NaA2+0.5B4+1.5O4 have been reported previously: NaCo0.5Ti1.5O4 and NaNi0.5Ti1.5O4. (35,36) Given the trends established by Reid et al., other combinations of metal cations should be possible. It was found that Co2+ and Ni2+ could be replaced by Mg2+ (JT-inactive) or Fe2+ (weakly JT-active). No CF phases formed when the compositions NaA2+0.5Ti1.5O4 (A2+ = Mn2+, Cu2+, and Zn2+) were targeted. That CF-NaCu0.5Ti1.5O4 could not be synthesized at ambient pressure is consistent with the conclusion made by Reid et al., as Cu2+ is strongly JT-active. However, Mn2+ (d5 electron configuration) and Zn2+ are not JT-active. Mn2+ is quite large (0.83 Å), and Fe2+ (0.78 Å) is the largest divalent cation successfully substituted in the NaA2+0.5Ti1.5O4 compositions. It is easy to conclude that the size mismatch between the divalent cation and Ti4+ becomes too large when A2+ = Mn2+, destabilizing the CF phase, but the results of the NaA2+0.5Sn1.5O4 system cast doubt on this explanation. On the other hand, Zn2+ has an ionic radius (0.74 Å) within the range of the divalent metals substituted into NaA2+0.5Ti1.5O4. It is possible that the preference of Zn2+ for tetrahedral sites destabilizes the CF structure. A compound with lower Na and Zn content in the Na–Zn–Ti–O system, freudenbergite-type Na1.84Zn0.92Ti7.08O16, does contain octahedrally coordinated Zn2+. (62) However, the Zn2+ content is dilute compared to the Ti4+ in the freudenbergite compound. Furthermore, the increased sodium content in the CF compound would be expected to increase the covalency of the Zn–O bonds. More covalent Zn–O bonds are expected to favor tetrahedrally coordinated Zn2+.
No compounds of the type NaA2+0.5Sn1.5O4 have been reported previously. Given the existence of NaA2+0.5Ti1.5O4 compounds and Na-CFs containing Sn4+ (NaFeSnO4), it seemed probable NaA2+0.5Sn1.5O4 would also be stable. Notably, more CF-NaA2+0.5Sn1.5O4 compounds were found than CF-NaA2+0.5Ti1.5O4 compounds, with Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ all forming Na-CF compounds when paired with Sn4+. As with NaMn3+SnO4, Sn4+ stabilizes the CF structure even when paired with the strongly JT-active Cu2+. Given the existence of NaMnSnO4 and NaCu0.5Sn1.5O4, it appears that spherical (JT-inactive) cations are not a necessary condition for a stable CF phase in the case of NaA2+0.5Sn1.5O4 and NaA3+SnO4. NaZn0.5Sn1.5O4 and NaMn0.5Sn1.5O4 can also be formed, unlike NaZn0.5Ti1.5O4 and NaMn0.5Ti1.5O4. It would be easy to conclude that NaMn0.5Sn1.5O4 forms because the difference in ionic radii between Sn4+ and Mn2+ is smaller than the difference between Ti4+ and Mn2+. However, we were also able to form NaCd0.5Sn1.5O4, and the difference in ionic radius between Cd2+ (0.95 Å) and Sn4+ (0.69 Å) is even larger than the difference between Mn2+ (0.83 Å) and Ti4+ (0.605 Å). The existence of NaCd0.5Sn1.5O4 makes Cd2+ the largest divalent framework cation known to occur in an Na-CF compound so far.
Clearly, Ti4+ and Sn4+ behave quite differently in the Na-CF phase space. Sn4+ stabilizes the CF structure more than Ti4+, as many of the cations that do not form a Na-CF with Ti4+ do form one when paired with Sn4+ instead, as is the case with NaMnSnO4, NaInSnO4, NaMn0.5Sn1.5O4, NaCu0.5Sn1.5O4, and NaZn0.5Sn1.5O4. The ability of Ti4+ to accommodate a high degree of octahedral distortion, owing to its unique combination of size and d0 electron configuration, (63−65) creates a large number of competing phases in the Ti systems not present in the Sn systems. For example, the Na2O–MgO–TiO2 phase diagram contains at least eight reported quaternary phases (including NaMg0.5Ti1.5O4), (52,66) whereas, to the best of our knowledge, the NaMg0.5Sn1.5O4 reported in this paper is the only known phase in the Na2O–MgO–SnO2 system. Since many of the phases containing highly distorted TiO6 octahedra do not have Sn4+ analogues, such as the freudenbergite structure, (67) it becomes more likely that the CF phase is on the thermodynamic convex hull in the Na2O–AO/A2O3–SnO2 systems. Another obvious difference between Ti4+ and Sn4+ is their ionic radii (0.605 and 0.69 Å, respectively). This difference was invoked by Chiring et al. to explain the stability of NaMnSnO4. (25) It was suggested Sn4+ exerted chemical pressure on Mn3+, stabilizing the octahedral configuration, as opposed to the square-pyramidal coordination observed in Na4Mn4Ti5O18. Alternatively, one could say the framework sites in NaMnSnO4 are larger than in the hypothetical NaMnTiO4, which enhances the stability of octahedral Mn3+. This reasoning might also be applied to NaZn0.5Sn1.5O4 to explain how pairing Zn2+ with Sn4+ achieves the desired octahedral coordination of Zn2+ instead of tetrahedral coordination. Notably, tetrahedral Zn2+ (0.60 Å) has a radius closer to that of octahedral Ti4+ (0.605 Å) than octahedral Sn4+ (0.69 Å), and octahedral Zn2+ (0.74 Å) has a radius closer to that of octahedral Sn4+ than octahedral Ti4+. Thus, mixing of Sn4+ with Zn2+ on octahedral sites seems more favorable, allowing for ZnO6 octahedra. However, it is difficult to say if the “stabilization” of the CF phase is not simply a result of the destabilization of competing phases such as Na4Mn4Ti5O18 upon Sn4+ substitution owing to the preference of Sn4+ for more symmetric octahedra or if both factors are important.
NaFe1.5Sb0.5O4 was the only reported Na-CF of the type NaA3+1.5B5+0.5O4. We found that CF phases also exist in the Na+-Sc3+-Sb5+-O2– and Na+-In3+-Sb5+-O2– systems. However, mixtures with the ideal compositions corresponding to NaSc1.5Sb0.5O4 and NaIn1.5Sb0.5O4 do not result in phase purity, at least under the synthetic conditions explored. In the case of Na1.16In1.18Sb0.66O4, some of the Na+ (1.02 Å) occupies the framework sites. It is likely the larger size of In3+ (0.800 Å) relative to Fe3+ (0.645 Å) allows the framework-site mixing. Sc3+ (0.745 Å) is somewhat smaller than In3+, which is consistent with “NaSc1.5Sb0.5O4” having a smaller degree of Na+ substitution on the octahedral sites. Interestingly, NaCr1.5Sb0.5O4 could not be prepared at either 900 or 950 °C. P3 phases in the Na1–xCr1–x/2Sbx/2O2 (0.42 ≤ x ≤ 0.5) system exist which are very close in composition to the target NaCr1.5Sb0.5O4, so it is likely the enhanced stability of highly Na-vacant layered phases is responsible for the absence of NaCr1.5Sb0.5O4. (68) In contrast, the layered Na1–xFe1–x/2Sbx/2O2 phase is stable only down to x = 0.25, and the CF phase is observed when lower x values are attempted. (69)
While solid solutions between NaScTiO4 and NaFeTiO4 have been successfully synthesized, to the best of our knowledge, no other Na-CF solid solutions have been reported to form via ambient-pressure synthesis. We successfully synthesized three NaA3+B4+O4–NaA2+0.5B4+1.5O4 compositions: NaCo1/3Fe1/3Ti4/3O4, NaNi1/3Sc1/3Ti4/3O4, and NaNi1/3Fe1/3Ti4/3O4. While other solid solutions were not attempted, these results suggest numerous solid solution series are accessible.
Given the results presented here and in the context of previous literature, we suggest that the phase space of Na-CFs might be expanded even more through hydrothermal synthesis by the introduction of more cation site order and stoichiometry nonhomogeneity. Some of the Na-CFs reported here show cation preference between the two framework sites, even though the compounds were quenched from high temperature. If these can be synthesized via hydrothermal synthesis, it is likely the degree of cation preference and sodium vacancies can be enhanced, as in the case of some of the Na0.55Fe0.28Ti1.72O4 and Na1–xFe1–xTi1+xO4. (38,57) More superstructures of the CF structure may also be discovered, such as in the case of Na3Mn4Te2O12, (39) and would be more likely when the framework cations have greater differences in charge density. Finally, some cation combinations that do not produce a CF at high temperature might be stabilized under, e.g., hydrothermal conditions.
The unit cell volumes for the new compounds range from 284.872(1) Å3 for Na0.99Cr0.99Ti1.01O4 to 341.995(17) Å3 for NaCd0.5Sn1.5O4. As would be expected, the unit cell volume generally increases as the weighted-average framework cation radius increases (see Figure 7 and Table 1). The Na–O bond lengths for the NaO8 bicapped trigonal prisms increase as the unit cell volume increases. For Na0.99Cr0.99Ti1.01O4, the Na–O bond lengths range from 2.378(1) Å to 2.568(1) Å. For NaNi0.5Sn1.5O4, with a unit cell volume of 323.483(2) Å3, the Na–O bond lengths range from 2.444(2) Å to 2.644(2) Å. For Na0.96Sn0.96Sn1.04O4, with a unit cell volume of 341.504(2) Å3, the Na–O bond lengths range from 2.472(2) Å to 2.728(3) Å (see Table S2). This may have implications for Na+ mobility.

Figure 7

Figure 7. Unit cell volume of the new Na-CFs versus the weighted-average effective ionic radius of the framework cations in octahedral coordination. (58)

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Comparison to Lithium Spinels

A natural comparison to Na-CF compounds are the lithium spinels. Since Li+ is smaller than Na+, it favors lower coordination numbers and shorter bond distances to oxygen, stabilizing the spinel structure as opposed to the CF structure. The spinel structure contains two primary cation sites, the tetrahedral 8a site and the octahedral 16d site. The octahedral sites comprise the framework; a 3D series of interconnected tunnels are formed by the occupied tetrahedral sites and empty octahedral 16c sites. Because Li+ can readily accommodate coordination numbers of four and six, it can occupy both the tetrahedral 8c and octahedral 16d sites. This results in antisite defects, or inversion, in which Li+ and another cation that does not have a high octahedral site preference are statically distributed among the 8c and 16d sites according to their relative site preferences. In contrast, this does not occur in Na-CFs to a measurable extent. While Na+, like Li+, varies in its coordination number and geometry for known materials and is known to occupy both 6- and 8-coordinate sites; the smaller, more highly charged cations like Ti4+ are not expected to occupy 8-coordinate sites except at very high pressures. In addition, the larger difference in size between Na+ and the CF framework cations relative to Li+ and spinel framework cations increases the site preferences. Thus, in LiFeTiO4, significant inversion is observed, with Li+ and Fe3+ essentially being randomly distributed. (70) In contrast, in NaFeTiO4, Na+ solely occupies the 8-coordinate tunnel sites, and Fe3+ and Ti4+ exclusively occupy the octahedral framework sites. (8) For energy storage applications, the lack of antisite defects in Na-CF’s is expected to be beneficial. (71) Inversion in spinels results in highly charged, immobile cations occupying the tetrahedral sites, which blocks the lowest energy diffusion path, hindering electrochemical performance. (72−74) This likely explains why spinel-LiFeTiO4, with a high degree of inversion, has both a high activation energy for ionic conduction and a low reversible specific capacity, (70,75) whereas CF-LiFeTiO4, synthesized by ion exchange from NaFeTiO4, nearly achieves theoretical capacity. (19) Furthermore, Na+ is known to be exchangeable with Li+ topotactically for some Na-CFs, meaning Li-CFs can be accessed at ambient pressure. (19,20,23)
The ability of Li+ to occupy both 4- and 6- coordinate sites can also be exploited to synthesize Li-rich spinels such as Li4Mn5O12 and Li4Ti5O12, in which Li+ occupies all tetrahedral positions and some of the octahedral framework sites as well. (54,55) Analogous Na-CFs, in which Na would occupy all the 8-coordinate tunnel sites and some of the octahedral sites, were previously unreported. Na1.16In1.18Sb0.66O4 appears to be the first such example, with ∼8% of the framework sites occupied by Na+, with Na–Sc–Sb–O and Na–Cd–Sn–O also appearing to be further phases with framework Na+. However, framework sodium appears to be nonexistent for Na-CFs with redox-active transition metal cations. This is likely because the redox-active transition metals found in CFs are significantly smaller than In3+/Cd2+/Sc3+, which decreases the average size of the framework sites.

Thermodynamic Calculations

Density functional theory (DFT) calculations were used to further understand the stability of phases in the Na-CF chemical space. The energy of the CF phase relative to the normal spinel phase (Fd3̅m) as well as the energy above the convex hull of stability, Ehull, for the CF phases were computed for various combinations of octahedral cations and at varying levels of sodiation. Combinations were chosen to include a range of successfully synthesized Na-CFs as well as compositions not expected to produce a CF phase (e.g., NaCrZrO4). Calculated Ehull values of the Na-CF phase at 0 K and without considering entropic effects are shown in Figure 8a. If the two octahedral sites are equivalently occupied by the A and B cations in the Na-CF phases, ideal mixing would suggest configurational entropy provides significant stabilization at 1200 K (the approximate synthesis temperature), lowering the energy by ∼21 meV/atom for the NaA3+B4+O4 compositions and ∼17 meV/atom for the NaA2+0.5B4+1.5O4 compositions. Figure 8b shows Ehull after including this configurational entropy contribution for fully sodiated compounds. Each box in this panel is colored according to the experimentally observed synthesis ability, with green boxes indicating successful synthesis, red boxes indicating failed synthesis, and no box indicating no known synthesis attempt. When including configurational entropy, 8 of the 12 synthesized postspinels are predicted to be on the convex hull (stable), with three more lying very close to the hull (<5 meV/atom). The notable exception is NaCo0.5Ti1.5O4, which is calculated to lie 13 meV/atom above the hull. Of the six compounds that could not be synthesized in the postspinel structure, NaMnTiO4 and NaRhSnO4 are predicted to be stable, while the others are predicted to be unstable with respect to decomposition into competing phases. The thermodynamic stability of NaMnTiO4 and NaRhSnO4, which could not be synthesized, and the thermodynamic instability of NaCo0.5Ti1.5O4 emphasizes the role of kinetics and metastability in the synthesis of these oxides. (76,77) We note that the calculated lack of stability of NaCo0.5Ti1.5O4 may arise from the inability to converge this structure with Co2+ in a high-spin state, as would be expected for CoO6 octahedra with Co2+ and was observed in our calculations for the other Co2+-containing CF phases (NaCo0.5Sn1.5O4 and NaCo0.5Zr1.5O4).

Figure 8

Figure 8. (a) Computed stability of NaxA3+B4+O4 and NaxA2+0.5B4+1.5O4 CF phases with three degrees of sodiation (x = 0, 0.5, 1.0). (b) Energy above hull of each xNa = 1 compound after including ideal mixing entropy for the octahedral cations at 1200 K. Green and red boxes show successful/failed syntheses at ambient pressure. (c) Energy difference between the CF and spinel structure. Note that the empty boxes correspond to In-containing compounds that failed to converge in either the CF or spinel structures and were consequently excluded from this analysis.

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No new CF compounds containing Zr4+ were successfully synthesized, which is consistent with the high Ehull values calculated for the CF phases containing Zr4+ (ranging from 26 meV/atom for NaMn0.5Zr1.5O4 to 71 meV/atom for NaCrZrO4). After factoring in configurational entropy for the CF phase at 1200 K, all CF phases with Zr still remain above the hull. The stability of NaA2+0.5Zr1.5O4 increases as the size of A2+ increases, and NaMn0.5Zr1.5O4 is only 9 meV/atom above the hull when factoring in configurational entropy. The large size of Zr4+ and its ability to have coordination numbers higher than six likely destabilizes the CF structure relative to competing phases including ZrO2, in which Zr is 7-fold coordinated. In each attempted synthesis of the NaA3+ZrO4 and NaA2+0.5Zr1.5O4 phases, baddeleyite ZrO2 or a higher symmetry, partially substituted ZrO2 phase is formed as the main phase. NaScZrO4 appears to be a special case and remains the only known Na-CF containing Zr4+. Sn4+- and Ti4+-containing compounds have lower Ehull than those with Zr4+, in agreement with experiments that found many possible combinations including Sn and Ti. Considering that Sn4+ (0.69 Å) and Zr4+ (0.72 Å) have similar effective ionic radii, the increased stability of Sn4+-containing CF phases might originate because Sn4+ prefers the octahedral site more than Zr4+ or from the prevalence of low-energy zirconium oxide competing phases. Some of the newly synthesized phases contain redox-active metals and may be of interest as battery electrode materials, so thermodynamic calculations were also used to explore the (in)stability of the CF phase upon desodiation (Figure 8a). As expected, removing the Na+ cations destabilizes the CF structure to some degree, with values for the completely desodiated CF phases ranging from 68 meV/atom for MnTiO4 to 234 meV/atom for Ni0.5Zr1.5O4. The stability of the empty CF framework was compared to the empty spinel framework of the same composition (Figure 8c). Interestingly, the empty CF structure is more stable in every case examined here. Spinels are well-studied as Li-battery electrodes. While the spinel anodes like LiTi2O4, Li4Ti5O12, and LiCrTiO4 perform well when additional lithium is inserted and re-extracted, (78,79) when full removal of the already-present Li+ is attempted, many lithium spinels either have limited capacity or show irreversible phase transitions that do not preserve the spinel lattice. This has been observed in LiTi2O4, LiV2O4, LiVTiO4, and LiCrTiO4. (79−82) The calculations presented here indicate the CF framework is more stable when fully charged than the spinel framework. In fact, the charged CF-CrTiO4 phase has an Ehull about one-half that of the charged spinel-CrTiO4 phase (98 meV/atom vs 195 meV/atom). Given the variety of CF phases explored in these calculations, this is likely a general phenomenon and may extend to many more if not all CF/spinel compositions. Thus, CF phases appear to be promising as energy storage materials.

Conclusions

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The phase space of Na-containing CaFe2O4-type compounds has been expanded to include 16 new compositions and several additional solid-solutions. Previously it was suggested that only cations without Jahn–Teller distortions (spherical cations) form CaFe2O4-type compounds with sodium in the tunnels, but the existence of NaMnSnO4 and NaCu0.5Sn1.5O4 shows that this “requirement” is relaxed when B4+ is Sn4+. However, tetravalent cations larger than Sn4+ do not effectively stabilize the CaFe2O4 structure, and NaScZrO4 and NaScHfO4 remain the only known Na-CFs when the tetravalent cation is larger than Sn4+. In most cases, the framework cations are randomly distributed among the two framework sites, but weak site preference was observed for NaMg0.5Ti1.5O4 and NaCu0.5Sn1.5O4. Only in one case did Rietveld refinement and 23Na NMR spectroscopy indicate strong site preference: the first known CaFe2O4-type compound with Na+ occupying framework sites, Na1.16In1.18Sb0.66O4. In this material, the large Na+ cation strongly prefers one of the two symmetrically distinct framework sites, suggesting the order is driven by differences in charge density. “NaSc1.5Sb0.5O4,” which always contained secondary phases, may also contain Na+ in the framework sites, albeit to a lesser degree than Na1.16In1.18Sb0.66O4. DFT calculations revealed that most of the successfully synthesized Na-CFs were on or near their respective convex hull, with the exception of NaCo0.5Ti1.5O4, whereas the hypothetical Na-CFs containing Zr4+ were much higher in energy, suggesting the Na-CF compounds containing Zr4+ are thermodynamically unstable. Additional DFT calculations show that the charged (desodiated) CF framework is more stable than a charged spinel framework of the same composition, suggesting an opportunity for postspinel phases as Li/Na/Mg electrode materials. Given the picture described here, the richness of this phase space can likely be further expanded by synthesizing solid solutions as well as using hydrothermal and other soft chemical methods. The growing library of CaFe2O4-type materials inspires future fundamental and applied studies on these materials and related phase spaces.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsorginorgau.1c00019.

  • Table of attempted syntheses and products, Rietveld refinements, additional 23Na NMR spectra, and table of Na–O bond distances for selected compounds (PDF)

Accession Codes

CCDC 2103718, 2103825–2103831, 2103833–2103835, 2103925, 2103928–2103929, 2103933, 2103935, and 2103938 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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Author Information

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  • Corresponding Author
    • Kenneth R. Poeppelmeier - Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States;  Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Orcidhttps://orcid.org/0000-0003-1655-9127;  Email: [email protected]
  • Authors
    • Justin C. Hancock - Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States;  Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Orcidhttps://orcid.org/0000-0002-3610-291X
    • Kent J. Griffith - Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States;  Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Orcidhttps://orcid.org/0000-0002-8096-906X
    • Yunyeong Choi - Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
    • Christopher J. Bartel - Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States;  Orcidhttps://orcid.org/0000-0002-5198-5036
    • Saul H. Lapidus - Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Orcidhttps://orcid.org/0000-0002-7486-4325
    • John T. Vaughey - Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States;  Orcidhttps://orcid.org/0000-0002-2556-6129
    • Gerbrand Ceder - Joint Center for Energy Storage Research, Argonne National Laboratory, Argonne, Illinois 60439, United States;  Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States;  Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States;  Orcidhttps://orcid.org/0000-0001-9275-3605
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This work made use of the Jerome B. Cohen X-ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (Grant DMR-1720139) at the Materials Research Center of Northwestern University and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (Grant NSF ECCS-2025633). This work made use of the IMSERC NMR facilities at Northwestern University, which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (Grant NSF ECCS-2025633), International Institute of Nanotechnology, and Northwestern University. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231. Computational resources were also provided by the Extreme Science and Engineering Discovery Environment (XSEDE) resource Stampede2 through Allocation TG-DMR970008S, which is supported by the National Science Foundation Grant Number ACI1053575.

References

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This article references 82 other publications.

  1. 1
    Bertraut, E.-F.; Blum, P.; Magnano, G. Structure des vanadite, chromite et ferrite monocalciques. Bull. Mineral. 1956, 79, 536– 561
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Hill, P. M.; Peiser, H. S.; Rait, J. R. The crystal structure of calcium ferrite and β calcium chromite. Acta Crystallogr. 1956, 9, 981– 986,  DOI: 10.1107/S0365110X56002862
    Google Scholar
    2
    The crystal structure of calcium ferrite and β-calcium chromite
    Hill, Patricia M.; Peiser, H. S.; Rait, J. R.
    Acta Crystallographica (1956), 9 (), 981-6CODEN: ACCRA9; ISSN:0365-110X.
    Burdese's (Malgnori and Cirilli, Proc. Intern. Symposium on Chem. Cements. 3rd Symposium, London, 1952) cell dimensions (a = 9.16 ± 0.03, b = 10.67 ± 0.03, c = 3.012 ± 0.006 A.) are confirmed for Ca ferrite, which is isomorphous with β-Ca chromite and probably with Sr ferrite, but his statement about the close-packed hexagonal arrangement of O atoms is disproved. The space group is Pnam. The solution of the still incompletely refined structure from Patterson synthesis, Fourier projection, and 3-dimensional Fourier section at z = 1/4 is described. The residual disagreement factor, R, is 22%, this high value being due partly to pseudosymmetry. The crystal chemistry of the compd. is briefly discussed in relation to some of its phys. properties. The coordinations of Ca and Fe ions are normal.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG2sXhsFCgtQ%253D%253D&md5=1ac15e20ae1c5699e26cfc3ed6152209
  3. 3
    Irifune, T.; Fujino, K.; Ohtani, E. A new high-pressure form of MgAl2O4. Nature 1991, 349, 409– 411,  DOI: 10.1038/349409a0
    Google Scholar
    3
    A new high-pressure form of magnesium aluminum spinel (MgAl2O4)
    Irifune, T.; Fujino, K.; Ohtani, E.
    Nature (London, United Kingdom) (1991), 349 (6308), 409-11CODEN: NATUAS; ISSN:0028-0836.
    The transformation of MgAl2O4 (I) spinel to a new high-pressure form at > 25 GPa in a multianvil high-pressure app. was studied. The new phase has a structure similar to that of CaFe2O4 (Ca ferrite) and its zero-pressure d. is 3.937(3) g/cm3, which is ∼2% denser than the lower-pressure assemblage of periclase + corundum. This high-pressure form of I may be an important host of Al in the Earth's lower mantle.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXhtVKhtro%253D&md5=bb39ceaf53fdb2322c3ab76d100fb651
  4. 4
    Funamori, N.; Jeanloz, R.; Nguyen, J. H.; Kavner, A.; Caldwell, W. A.; Fujino, K.; Miyajima, N.; Shinmei, T.; Tomioka, N. High-pressure transformations in MgAl2O4. J. Geophys. Res. Solid Earth 1998, 103, 20813– 20818,  DOI: 10.1029/98JB01575
    Google Scholar
    4
    High-pressure transformations in MgAl2O4
    Funamori, Nobumasa; Jeanloz, Raymond; Nguyen, Jeffrey H.; Kavner, Abby; Caldwell, Wendel A.; Fujino, Kiyoshi; Miyajima, Nobuyoshi; Shinmei, Toru; Tomioka, Naotaka
    Journal of Geophysical Research, [Solid Earth] (1998), 103 (B9), 20813-20818CODEN: JGEREE; ISSN:1934-8843. (American Geophysical Union)
    X ray diffraction and transmission electron microscopy on laser-heated diamond cell samples show that with increasing pressure MgAl2O4 spinel transforms first to Al2O3 corundum + MgO periclase, then to the CaFe2O4-structured phase, and finally to a new phase having the CaTi2O4 structure above ∼40 GPa. The CaFe2O4 and the CaTi2O4 structures are closely related and have almost the same densities and bulk moduli. Transformation from the CaFe2O4 to the CaTi2O4 phase would be expected to take place in oceanic crust that is subducted deep into the lower mantle.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmtFKlsLY%253D&md5=0fa84f0818ba0293dc51961ef76e5b15
  5. 5
    Liu, L. High pressure NaAlSiO4: the first silicate calcium ferrite isotype. Geophys. Res. Lett. 1977, 4, 183– 186,  DOI: 10.1029/GL004i005p00183
    Google Scholar
    5
    High pressure sodium aluminum silicate: the first silicate calcium ferrite isotype
    Liu, Lin-Gun
    Geophysical Research Letters (1977), 4 (5), 183-6CODEN: GPRLAJ; ISSN:0094-8276.
    At 100-180 kbars and ∼1000°, nepheline disproportionates into a mixt. of jadeite and α-NaAlO2. At >180 kbars, new x-ray diffraction lines began to appear and at 280 kbars, the sample was completely converted to the new phase. At >180 kbars, the mixt. of jadeite and α-NaAlO2 is inferred to react to form the Ca ferrite-type NaAlSiO4. It is the most closely packed A2SiO4 compd. known to date and appears to be the most likely host for Na in the earth's deep mantle.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2sXlt1Smur8%253D&md5=f16a4d7f1e37aa15f39bed610da697c9
  6. 6
    Yamada, H.; Matsui, Y.; Ito, E. Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure. Mineral. Mag. 1983, 47, 177– 181,  DOI: 10.1180/minmag.1983.047.343.07
    Google Scholar
    6
    Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure
    Yamada, Hirohisa; Matsui, Yoshito; Ito, Eiji
    Mineralogical Magazine (1983), 47 (343), 177-81CODEN: MNLMBB; ISSN:0026-461X.
    A high-pressure modification of NaAlSiO4 with Ca-ferrite structure was synthesized at > 24 GPa. The unit-cell dimensions are a ∼ 10.1546, h ∼ 8.6642, c ∼ 2.7385 Å, and V ∼ 24.93 Å3, with space group Pbnm. The calcd. d. is ∼ 3.916 g/cm3. Both M1O6 and M2O6 octahedra run parallel to the c axis, forming edge-shared double chains. The shared edges exhibit remarkable shortening (2.25-2.39 Å). Na atoms are located in the tunnel-type structure formed by the linked double chains being in 8-fold coordinations. The possible instability of the Ca-ferrite Mg2SiO4 is discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3sXhvVaktr0%253D&md5=92fa4dd594d860eba7105050a499d400
  7. 7
    Reid, A. F.; Wadsley, A. D.; Ringwood, A. E. High pressure NaAlGeO4, a calcium ferrite isotype and model structure of silicates at depth in the earth’s mantle. Acta Crystallogr. 1967, 23, 736– 739,  DOI: 10.1107/S0365110X67003627
    Google Scholar
    7
    High pressure sodium aluminum germanate a calcium ferrite isotype and model structure for silicates at depth in the earth's mantle
    Reid, Allen Forrest; Wadsley, Arthur D.; Ringwood, Alfred E.
    Acta Crystallographica (1967), 23 (5), 736-9CODEN: ACCRA9; ISSN:0365-110X.
    The high pressure phase NaAlGeO4 formed at 120 kilobars and 900° has the Ca ferrite structure, space group Pnma, unit-cell dimensions a 8.87, b 2.84, c 10.40 A.; dx is 4.73. The isomorphous silicate NaAlSiO4 (dx = 3.9 ± 0.1), should exist in the earth's mantle, being transformed by pressure from nepheline or jadeite.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXnt1Gm&md5=bc418c5a7604be4ec1af4f76aa040fab
  8. 8
    Reid, A. F.; Wadsley, A. D.; Sienko, M. J. Crystal chemistry of sodium scandium titanate, NaScTiO4, and its isomorphs. Inorg. Chem. 1968, 7, 112– 118,  DOI: 10.1021/ic50059a024
    Google Scholar
    8
    Crystal chemistry of sodium scandium titanate, NaScTiO4, and its isomorphs
    Reid, Allen Forrest; Wadsley, Arthur D.; Sienko, Michell J.
    Inorganic Chemistry (1968), 7 (1), 112-18CODEN: INOCAJ; ISSN:0020-1669.
    NaScTiO4, NaFeTiO4, NaScSnO4, NaFeSnO4, NaScZrO4, and NaScHfO4, as well as high-pressure NaAlGeO, are strictly isomorphous with the orthorhombic Ca ferrite type structure, space group Pnma. Each pair of tri-and quadrivalent elements randomly occupies two sets of crystallographically nonequiv. octahedral positions in the structure, the local site symmetries of which are almost identical. Uniform bond lengths and normal thermal vibration parameters for the randomized atoms in NaScTiO4, detd. by single-crystal structure analysis, are interpreted to mean that the randomness of the ions Sc3+ and Ti4+ leads to a real averaging of ionic sizes. No Ca ferrite structure was found by replacing Na with Li, K, Rb, or Cs nor for the NaA3+B4+O4 compds. where A3+ = Mn, Cr, Co, or In, although a no. of other phases were formed. Ca ferrite isotypes form only when A3+ and B4+ can be constrained to match one another both in size and in a local site symmetry which is nearly spherical. 45 references.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXjsVSjtw%253D%253D&md5=a166fffe498225dc0745f669c7e52df8
  9. 9
    Ishii, T.; Sakai, T.; Kojitani, H.; Mori, D.; Inaguma, Y.; Matsushita, Y.; Yamaura, K.; Akaogi, M. High-pressure phase relations and crystal structures of postpinel phases in MgV2O4, FeV2O4, and MnCr2O4: crystal chemistry of AB2O4 postspinel compounds. Inorg. Chem. 2018, 57, 6648– 6657,  DOI: 10.1021/acs.inorgchem.8b00810
    Google Scholar
    9
    High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds
    Ishii, Takayuki; Sakai, Tsubasa; Kojitani, Hiroshi; Mori, Daisuke; Inaguma, Yoshiyuki; Matsushita, Yoshitaka; Yamaura, Kazunari; Akaogi, Masaki
    Inorganic Chemistry (2018), 57 (11), 6648-6657CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    We have investigated high-pressure, high-temp. phase transitions of spinel (Sp)-type MgV2O4, FeV2O4, and MnCr2O4. At 1200-1800 °C, MgV2O4 Sp decomps. at 4-7 GPa into a phase assemblage of MgO periclase + corundum (Cor)-type V2O3, and they react at 10-15 GPa to form a phase with a calcium titanite (CT)-type structure. FeV2O4 Sp transforms to CT-type FeV2O4 at 12 GPa via decompn. phases of FeO wustite + Cor-type V2O3. MnCr2O4 Sp directly transforms to the calcium ferrite (CF)-structured phase at 10 GPa and 1000-1400 °C. Rietveld refinements of CT-type MgV2O4 and FeV2O4 and CF-type MnCr2O4 confirm that both the CT- and CF-type structures have frameworks formed by double chains of edge-shared B3+O6 octahedra (B3+ = V3+ and Cr3+) running parallel to one of orthorhombic cell axes. A relatively large A2+ cation (A2+ = Mg2+, Fe2+, and Mn2+) occupies a tunnel-shaped space formed by corner-sharing of four double chains. Effective coordination nos. calcd. from eight neighboring oxygen-A2+ cation distances of CT-type MgV2O4 and FeV2O4 and CF-type MnCr2O4 are 5.50, 5.16, and 7.52, resp. This implies that the CT- and CF-type structures practically have trigonal prism (six-coordinated) and bicapped trigonal prism (eight-coordinated) sites for the A2+ cations, resp. A relationship between cation sizes of VIIIA2+ and VIB3+ and crystal structures (CF- and CT-types) of A2+B23+O4 is discussed using the above new data and available previous data of the postspinel phases. We found that CF-type A2+B23+O4 crystallize in wide ionic radius ranges of 0.9-1.4 Å for VIIIA2+ and 0.55-1.1 Å for VIB3+, whereas CT-type phases crystallize in very narrow ionic radius ranges of ∼0.9 Å for VIIIA2+ and 0.6-0.65 Å for VIB3+. This would be attributed to the fact that the tunnel space of CT-type structure is geometrically less flexible due to the smaller coordination no. for A2+ cation than that of CF-type.
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  10. 10
    Yamaura, K.; Huang, Q.; Zhang, L.; Takada, K.; Baba, Y.; Nagai, T.; Matsui, Y.; Kosuda, K.; Takayama-Muromachi, E. Spinel-to-CaFe2O4-type structural transformation in LiMn2O4 under higher pressure. J. Am. Chem. Soc. 2006, 128, 9448– 9456,  DOI: 10.1021/ja0612302
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    10
    Spinel-to-CaFe2O4-Type Structural Transformation in LiMn2O4 under High Pressure
    Yamaura, Kazunari; Huang, Qingzhen; Zhang, Lianqi; Takada, Kazunori; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Kosuda, Kosuke; Takayama-Muromachi, Eiji
    Journal of the American Chemical Society (2006), 128 (29), 9448-9456CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A new form of LiMn2O4 is reported. The structure is the CaFe2O4-type and 6% denser than the spinel. The structure transformation was achieved by heating at 6 GPa. Anal. of the neutron diffraction pattern confirmed an av. of the structure; the unit cell was orthorhombic at a 8.8336(5), b 2.83387(18), and c 10.6535(7) Å (Pnma). Electron diffraction patterns indicated an order of superstructure 3a × b × c, which might be initiated by Li vacancies. The exact compn. is estd. at Li0.92Mn2O4 from the structure anal. and quantity of intercalated Li. The polycryst. CaFe2O4-type compd. showed semiconducting-like characters over the studied range >5 K. The activation energy was reduced to ∼0.27 eV from ∼0.40 eV at the spinel form, suggesting a possible enhancement of hopping mobility. Magnetic and specific-heat data indicated a magnetically glassy transition at ∼10 K. As the CaFe2O4-type transition was obsd. for the mineral MgAl2O4, hence the new form of the Li Mn oxide would provide valuable opportunities to study not only the magnetism of strongly correlated electrons but also the thermodn. of the phase transition in the mantle.
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  11. 11
    Yamaura, K.; Arai, M.; Sato, A.; Karki, A. B.; Young, D. P.; Movshovich, R.; Okamoto, S.; Mandrus, D.; Takayama-Muromachi NaV2O4: a quasi-1D metallic antiferromagnet with half-metallic chains. Phys. Rev. Lett. 2007, 99, 196601,  DOI: 10.1103/PhysRevLett.99.196601
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    11
    NaV2O4: A Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains
    Yamaura, K.; Arai, M.; Sato, A.; Karki, A. B.; Young, D. P.; Movshovich, R.; Okamoto, S.; Mandrus, D.; Takayama-Muromachi, E.
    Physical Review Letters (2007), 99 (19), 196601/1-196601/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    NaV2O4 crystals were grown under high pressure using a NaCl flux, and the crystals were characterized with x-ray diffraction, elec. resistivity, heat capacity, and magnetization. The structure of NaV2O4 consists of double chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic, with the resistivity perpendicular to the chains >20 times greater than that parallel to the chains. Magnetically, the intrachain interactions are ferromagnetic and the interchain interactions are antiferromagnetic; 3-dimensional antiferromagnetic order is established at 140 K. First-principles electronic structure calcns. indicate that the chains are half-metallic. The case of NaV2O4 seems to be a quasi-1D analog of what was found for half-metallic materials.
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  12. 12
    Sakurai, H.; Kolodiazhnyi, T.; Michiue, Y.; Takayama-Muromachi, E.; Tanabe, Y.; Kikuchi, H. Unconventional colossal magnetoresistance in sodium chromium oxide with a mixed-valence state. Angew. Chem. 2012, 124, 6757– 6760,  DOI: 10.1002/ange.201201884
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  13. 13
    Young, O.; Wildes, A. R.; Manuel, P.; Ouladdiaf, B.; Khalyavin, D. D.; Balakrishnan, G.; Petrenko, O. A. Highly frustrated magnetism in SrHo2O4: coexistence of two types of short-range order. Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 88, 024411,  DOI: 10.1103/PhysRevB.88.024411
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    13
    Highly frustrated magnetism in SrHo2O4. Coexistence of two types of short-range order
    Young, O.; Wildes, A. R.; Manuel, P.; Ouladdiaf, B.; Khalyavin, D. D.; Balakrishnan, G.; Petrenko, O. A.
    Physical Review B: Condensed Matter and Materials Physics (2013), 88 (2), 024411/1-024411/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    SrHo2O4 is a geometrically frustrated magnet in which the magnetic Ho3+ ions form honeycomb layers connected through a network of zigzag chains. At low-temp. 2 distinct types of short-range magnetic order can be inferred from single-crystal diffraction data, collected using both polarized and unpolarized neutrons. In the (hk0) plane the diffuse scattering is most noticeable around the k = 0 positions and its intensity rapidly increases at temps. below 0.7 K. In addn., planes of diffuse scattering at Q = (hk ± 1/2) are visible at temps. as high as 4.5 K. These planes coexist with the broad peaks of diffuse scattering in the (hk0) plane at low temps. Correlation lengths assocd. with the broad peaks are L ≈ 150 Å in the a-b plane and L ≈ 190 Å along the c axis, while the correlation length assocd. with the diffuse scattering planes is L ≈ 230 Å along the c axis at the lowest temp. Both types of diffuse scattering are elastic in nature. The highly unusual coexistence of the two types of diffuse scattering in SrHo2O4 is likely to be the result of the presence of two crystallog. inequivalent sites for Ho3+ in the unit cell.
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  14. 14
    Dutton, S. E.; Broholm, C. L.; Cava, R. J. Divergent effects of static disorder and hole doping in geometrically frustrated β-CaCr2O4. J. Solid State Chem. 2010, 183, 1798– 1804,  DOI: 10.1016/j.jssc.2010.05.032
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    14
    Divergent effects of static disorder and hole doping in geometrically frustrated β-CaCr2O4
    Dutton, S. E.; Broholm, C. L.; Cava, R. J.
    Journal of Solid State Chemistry (2010), 183 (8), 1798-1804CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
    The gallium substituted and calcium deficient variants of geometrically frustrated β-CaCr2O4, β-CaCr2-2xGa2xO4 (0.02≤x≤0.25) and β-Ca1-yCr2O4 (0.075≤y≤0.15), were studied by x-ray powder diffraction, magnetization and sp. heat measurements. This allows for a direct comparison of the effects, in a geometrically frustrated magnet, of the static disorder that arises from nonmagnetic substitution and the dynamic disorder that arises from hole doping. In both cases, disturbing the Cr3+ lattice results in a redn. in the degree of magnetic frustration. On substitution of Ga, which introduces disorder without creating holes, a gradual release of spins from ordered antiferromagnetic states is obsd. In contrast, in the calcium-deficient compds. the introduction of holes induces static ferrimagnetic ordering and much stronger perturbations of the β-CaCr2O4 host.
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  15. 15
    Arévalo-López, Á. M.; Dos santos-García, A. J.; Castillo-Martínez, E.; Durán, A.; Alario-Franco, M. Á. Spinel to CaFe2O4 transformation: Mechanism and properties of β-CdCr2O4. Inorg. Chem. 2010, 49, 2827– 2833,  DOI: 10.1021/ic902228h
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    15
    Spinel to CaFe2O4 Transformation: Mechanism and Properties of β-CdCr2O4
    Arevalo-Lopez, Angel M.; Dos santos-Garcia, Antonio J.; Castillo-Martinez, Elizabeth; Duran, Alejandro; Alario-Franco, Miguel A.
    Inorganic Chemistry (2010), 49 (6), 2827-2833CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    The CdCr2O4 spinel transforms to a 10.6% denser new polymorph of the CaFe2O4-type structure at 10 GPa and 1100°. This new polymorph has a honeycomb-like structure because of double rutile-type chains formed by [Cr-O6] edge-shared octehedra. This crystal structure is prone to be magnetically frustrated and presents low-dimensional antiferromagnetism at 25 K < T < 150 K, accompanied by more complex interactions as the temp. decreases. These transitions are evidenced by magnetic susceptibility and heat capacity measurements. We also discuss a possible structural mechanism for the transformation.
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  16. 16
    Shimomura, Y.; Kurushima, T.; Kijima, N. Photoluminescence and crystal structure of green-emitting phosphor CaSc2O4:Ce3+. J. Electrochem. Soc. 2007, 154, J234,  DOI: 10.1149/1.2741172
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    16
    Photoluminescence and Crystal Structure of Green-Emitting Phosphor CaSc2O4:Ce3+
    Shimomura, Yasuo; Kurushima, Tomoyuki; Kijima, Naoto
    Journal of the Electrochemical Society (2007), 154 (8), J234-J238CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    A new green phosphor, Ce3+-act5ivated CaSc2O4, was developed, which shows green luminescence with a peak wavelength of 515 nm under excitation with blue light. Ce3+-activated CaSc2O4 can be used as a material for color conversion of white-light-emitting diodes (LEDs), which consist of a blue LED, a green phosphor, and a red phosphor, because the luminescence efficiency of this phosphor is comparable to those of com. phosphors such as Y3Al5O12:Ce3+. The host crystal of this phosphor has an orthorhombic CaFe2O4 structure, and the Ce ion probably exists in an eight-coordinated Ca position. The authors studied the dependency of the firing temp. and dopant concn. for luminescence intensity and found that the optimum temp. and concn. were 1600° and 1 mol % of Ce substituted to the Ca position. The luminescence peak wavelength was shifted toward longer wavelengths by replacing Ca with Mg. In contrast, replacing Ca with Sr resulted in a shift toward shorter wavelengths.
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  17. 17
    Hao, Z.; Zhang, J.; Zhang, X.; Lu, S.; Wang, X. Blue-green-emitting phosphor CaSc2O4:Tb3+: tunable luminescence manipulated by cross-relaxation. J. Electrochem. Soc. 2009, 156, H193,  DOI: 10.1149/1.3060382
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    17
    Blue-Green-Emitting Phosphor CaSc2O4:Tb3+: Tunable Luminescence Manipulated by Cross-Relaxation
    Hao, Zhendong; Zhang, Jiahua; Zhang, Xia; Lu, Shaozhe; Wang, Xiaojun
    Journal of the Electrochemical Society (2009), 156 (3), H193-H196CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    Blue-green CaSc2O4:Tb3+ phosphors were prepd. by solid-state reaction. Under 254 or 276 nm light excitation, both blue and green emissions are obsd., which are attributed to the characteristic 4f-4f transitions (5D3,4-7FJ, J = 6, 5, 4, 3) of Tb3+. The cross-relaxation from 5D3 to 5D4 states are studied by spectroscopic and dynamic measurements. The luminescent color of CaSc2O4:Tb3+ can be tuned from blue to green by manipulating the cross-relaxation. Also, efficient white light is generated for fluorescence lamps by blending the blue-green CaSc2O4:Tb3+ with a red CaSc2O4:Eu3+ phosphor.
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  18. 18
    Hao, Z.; Zhang, J.; Zhang, X.; Wang, X. CaSc2O4:Eu3+: A tunable full-color emitting phosphor for white light emitting diodes. Opt. Mater. 2011, 33, 355– 358,  DOI: 10.1016/j.optmat.2010.09.035
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    18
    CaSc2O4:Eu3+: A tunable full-color emitting phosphor for white light emitting diodes
    Hao, Zhendong; Zhang, Jiahua; Zhang, Xia; Wang, Xiaojun
    Optical Materials (Amsterdam, Netherlands) (2011), 33 (3), 355-358CODEN: OMATET; ISSN:0925-3467. (Elsevier B.V.)
    We report an intense full-color emission originating from 5D0,1,2,3 to 7F0,1,2,3,4 transitions of Eu3+ in CaSc2O4 upon 395 nm excitation. The emission spectra vary with increasing Eu3+ concn., demonstrating tunable color coordinates from white to red region in the CIE chromaticity diagram. Considering the relaxation from 5DJ to 5DJ -1 through cross energy transfer, the Eu3+ concn. dependent emission spectra are well simulated based on the anal. of steady state rate equations and the measured lifetimes of the 5DJ levels. It is suggested that CaSc2O4:Eu3+ could be a potential single-phased full-color emitting phosphor for near-UV InGaN chip pumped white light emitting diodes.
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  19. 19
    Bruno, S. R.; Blakely, C. K.; Clapham, J. B.; Davis, J. D.; Bi, W.; Alp, E. E.; Poltavets, V. V. Synthesis and electrochemical properties of novel LiFeTiO4 and Li2FeTiO4 polymorphs with the CaFe2O4-type structures. J. Power Sources 2015, 273, 396– 403,  DOI: 10.1016/j.jpowsour.2014.09.115
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    19
    Synthesis and electrochemical properties of novel LiFeTiO4 and Li2FeTiO4 polymorphs with the CaFe2O4-type structures
    Bruno, Shaun R.; Blakely, Colin K.; Clapham, Jonathon B.; Davis, Joshua D.; Bi, Wenli; Alp, E. Ercan; Poltavets, Viktor V.
    Journal of Power Sources (2015), 273 (), 396-403CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    The new LiFeTiO4 polymorph with the CaFe2O4-type (CF) crystal structure was synthesized via ion exchange from NaFeTiO4. Due to the presence of tunnels sufficiently large to accommodate addnl. Li+ ions, CF-LiFeTiO4 was studied as a model compd. for potential cathode material utilizing Fe2+/Fe3+ (on Li intercalation) as well as Fe3+/Fe4+ (on Li deintercalation) redox couples. Chem. and electrochem. Li intercalation preserves the structural motif of CF-LiFeTiO4 and results in Li2FeTiO4 compd. The electrochem. cycling of CF-LiFeTiO4 vs. Li occurs between 2 and 2.3 V with an initial specific capacity of 148 mA-h/g. High Li+ ionic cond. in the compd. is suggested based on the interconnection of Li+ bond valence sum isosurfaces at a bond valence sum value of 1.0. Chem. Li deintercalation from CF-LiFeTiO4 results in compd. decompn. without Fe4+ formation, as confirmed by Moessbauer spectroscopy.
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  20. 20
    Jung, Y. H.; Kim, D. K.; Hong, S.-T. Synthesis, structure, and electrochemical Li-ion intercalation of LiRu2O4 with CaFe2O4-type structure. J. Power Sources 2013, 233, 285– 289,  DOI: 10.1016/j.jpowsour.2013.01.119
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    20
    Synthesis, structure, and electrochemical Li-ion intercalation of LiRu2O4 with CaFe2O4-type structure
    Jung, Young Hwa; Kim, Do Kyung; Hong, Seung-Tae
    Journal of Power Sources (2013), 233 (), 285-289CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    A new material, LiRu2O4, has been synthesized by ion-exchange reaction from NaRu2O4 that has been prepd. by solid state reaction at 950° under Ar flow. The crystal structure of LiRu2O4, isostructural with the parent NaRu2O4, has been refined by an x-ray Rietveld method (Pnma, a = 9.13940(5) Å, b = 2.80070(9) Å, c = 11.0017(1) Å, Z = 4, Rp = 5.30%, wRp = 6.73%, χ2 = 0.41, 23°). The structure belongs to CaFe2O4-type, where double chains of edge-sharing octahedral RuO6 share the corners with neighboring double chains and form tunnels in between them parallel to the shortest b-axis so that the one-dimensional Li array is placed inside each of the tunnels. Detailed structural anal. indicates that the tunnel inside has more than enough space to be filled with the Li atoms. The electrochem. tests of LiRu2O4 demonstrates a reversible Li intercalation reaction at 3.2-3.5 V vs. Li/Li+ with a capacity of ∼80 mA-h/g. The material exhibits excellent high-rate characteristics (93% capacity retention at 10C/1C) as well as high capacity retention with cycles (99% at 50 cycles).
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  21. 21
    Sun, X.; Blanc, L.; Nolis, G. M.; Bonnick, P.; Cabana, J.; Nazar, L. F. NaV1.25Ti0.75O4: a potential post-spinel cathode material. Chem. Mater. 2018, 30, 121– 128,  DOI: 10.1021/acs.chemmater.7b03383
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    NaV1.25Ti0.75O4: A Potential Post-Spinel Cathode Material for Mg Batteries
    Sun, Xiaoqi; Blanc, Lauren; Nolis, Gene M.; Bonnick, Patrick; Cabana, Jordi; Nazar, Linda F.
    Chemistry of Materials (2018), 30 (1), 121-128CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Rechargeable Mg batteries are promising candidates for high energy d. storage in theory, when a Mg metal anode is combined with an oxide cathode material. Despite the widely obsd. sluggish Mg2+ diffusion in most oxide lattices, recent first-principles calcns. predicted low diffusion barriers in the calcium ferrite (CF)-type post-spinel structures. In the present work, we exptl. examine the prospect of CF-type NaV1.25Ti0.75O4 as a Mg cathode. The Na+ ions, which lie in the ion migration pathway, need to be removed or exchanged with Mg2+ to allow Mg2+ de/intercalation. Partial desodiation was achieved through chem. and electrochem. methods, as proven by X-ray diffraction and X-ray absorption spectroscopy, but deep desodiation was accompanied by partial amorphization of the material. Mg2+ ion exchange at moderate temp. (80 °C) resulted in the formation of Na0.19Mg0.41V1.25Ti0.75O4; however, phase transformation was obsd. when higher temps. were applied to attempt complete ion exchange. Such phenomena point to the instability of the CF lattice when the tunnel is empty or occupied by a small ion (Mg2+). Thus, while the low migration barrier predicted by computation is partly based on the relative metastability of the theor. CF-MgxV1.25Ti0.75O4 lattice, the difficulty in stabilizing it also renders the material synthetically nonaccessible, hindering this post-spinel's application as an electrode material.
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  22. 22
    Mukai, K.; Uyama, T.; Yamada, I. Structural and electrochemical analyses on the transformation of CaFe2O4-type LiMn2O4 from spinel-type LiMn2O4. ACS Omega 2019, 4, 6459– 6467,  DOI: 10.1021/acsomega.9b00588
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    22
    Structural and Electrochemical Analyses on the Transformation of CaFe2O4-Type LiMn2O4 from Spinel-Type LiMn2O4
    Mukai, Kazuhiko; Uyama, Takeshi; Yamada, Ikuya
    ACS Omega (2019), 4 (4), 6459-6467CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
    Lithium manganese oxides have received much attention as pos. electrode ma- terials for lithium-ion batteries. In this study, a post-spinel material, CaFe2O4-type LiMn2O4 (CF-LMO), was synthesized at high pressures above 6 GPa, and its crystal structure and electrochem. properties were examd. CF-LMO exhibits a one- dimensional (1D) conduction pathway for Li ions, which is predicted to be superior to the three-dimensional conduction pathway for these ions. The stoichiometric LiMn2O4 spinel (SP-LMO) was decompd. into three phases of Li2MnO3, MnO2, and Mn2O3 at 600° C, and then started to transform into the CF-LMO structure above 800° C. The rechargeable capacity (Qrecha) of the sample synthesized at 1000° C was limited to 40 mAhg1 in the voltage range between 1.5 and 5.3 V, due to the presence of a small amt. of Li2MnO3 phase in the sample (= 9.1 wt%). In addn., the Li-rich spinels, Li[LixMn2x]O4 with x = 0.1, 0.2, and 0.333, were also employed for the synthesis of CF-LMO. The sample prepd. from x = 0.2 exhibited a Qrecha value exceeding 120 mAhg1 with stable cycling performance, despite the presence of large amts. of the phases Li2MnO3, MnO2, and Mn2O3. Details of the structural transformation from SP-LMO to CF-LMO and the effect of Mn ions on the 1D conduction pathway are discussed.
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  23. 23
    Nolis, G.; Gallardo-Amores, J. M.; Serrano-Sevillano, J.; Jahrman, E.; Yoo, H. D.; Hu, L.; Hancock, J. C.; Bolotnikov, J.; Kim, S.; Freeland, J. W.; Liu, Y.-S.; Poeppelmeier, K. R.; Seidler, G. T.; Guo, J.; Alario-Franco, M. A.; Casas-Cabanas, M.; Morán, E.; Cabana, J. Factors defining the intercalation electrochemistry of CaFe2O4-type manganese oxides. Chem. Mater. 2020, 32, 8203– 8215,  DOI: 10.1021/acs.chemmater.0c01858
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    Factors Defining the Intercalation Electrochemistry of CaFe2O4-Type Manganese Oxides
    Nolis, Gene; Gallardo-Amores, Jose M.; Serrano-Sevillano, Jon; Jahrman, Evan; Yoo, Hyun Deog; Hu, Linhua; Hancock, Justin C.; Bolotnikov, Jannie; Kim, Soojeong; Freeland, John W.; Liu, Yi-Sheng; Poeppelmeier, Kenneth R.; Seidler, Gerald T.; Guo, Jinghua; Alario-Franco, Miguel A.; Casas-Cabanas, Montse; Moran, Emilio; Cabana, Jordi
    Chemistry of Materials (2020), 32 (19), 8203-8215CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Oxides with the CaFe2O4-type structure were predicted as being suitable hosts for reactions of intercalation of light cations such as Li and Mg because of their favorable cationic diffusion. Although Li was shown to intercalate into the Mn2O4 variant, the key structure property correlations detg. function are not fully ascertained. This basic information is needed before attempting the intercalation of divalent cations, which face comparably higher migration barriers. For this purpose, the electrode function of CaFe2O4-type Li0.8Mn2O4 was compared for materials made by a direct high-pressure route or through cation exchange from NaMn2O4. X-ray diffraction and absorption spectroscopy revealed that, despite having largely the same bulk structure, the presence of surface defects blocked Li+ transfer in Li0.8Mn2O4 made at high pressure. These defects were not present in the cation-exchanged material, which resulted in highly reversible Li intercalation with very fast kinetics in micrometric crystals. Delithiated electrodes from the cation-exchange synthesis were subsequently reduced in an ionic liq. electrolyte contg. Mg2+. The process induced topotactic changes in the bulk, strongly suggesting the existence of intercalation, but it is accompanied by severe reactivity with the electrolyte that impedes reversibility. This study uncovers that defects affect the fundamentals of cation intercalation in this novel class of materials. The ability of the cation-exchanged material to conduct fast reactions with Li is consistent with calcd. activation energy barriers and creates promise for their use as Mg hosts, provided that novel electrolytes enhanced stability at high potential can be realized.
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  24. 24
    Liu, X.; Wang, X.; Iyo, A.; Yu, H.; Li, D.; Zhou, H. High stable post-spinel NaMn2O4 cathode of sodium ion battery. J. Mater. Chem. A 2014, 2, 14822– 14826,  DOI: 10.1039/C4TA03349C
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    24
    High stable post-spinel NaMn2O4 cathode of sodium ion battery
    Liu, Xizheng; Wang, Xi; Iyo, Akira; Yu, Haijun; Li, De; Zhou, Haoshen
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (36), 14822-14826CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    A spinel-type NaMn2O4 based on an inventive Mn and Na compd. was synthesized under high pressure (4.5 GPa) for use as the cathode of a Na ion battery. It exhibits a 1-step voltage profile, limited polarization and good capacity retention both at room and high temps. The capacity retention is 94% after 200 cycles at room temp. The stable battery performance is due to the high barrier of structure rearrangement and suppressed Jahn-Teller distortions in this post spinel structure.
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  25. 25
    Chiring, A.; Senguttuvan, P. Chemical pressure-stabilized post spinel-NaMnSnO4 as potential cathode for sodium-ion batteries. Bull. Mater. Sci. 2020, 43, 306,  DOI: 10.1007/s12034-020-02203-6
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    25
    Chemical pressure-stabilized post spinel-NaMnSnO4 as potential cathode for sodium-ion batteries
    Chiring, Aditi; Senguttuvan, Premkumar
    Bulletin of Materials Science (2020), 43 (1), 306CODEN: BUMSDW; ISSN:0250-4707. (Indian Academy of Sciences)
    Spinel LiMn2O4 is a popular cathode material in lithium-ion batteries due to its high operating voltage and reversible specific capacity. Synthesizing analogus NaMn2O4 in the spinel structure, for sodium-ion batteries, is challenging due to the thermodn. instability of the compd., mostly arising due to Jahn-Teller distortion of the Mn3+ center. However, post-spinel NaMn2O4 (named as such because the compds. were initially achieved by subjecting a spinel phase to high pressure) could be synthesized at a high temp. and pressure (1373 K and 4.5 GPa, resp.) and is found to be stable at std. conditions. Also, these compds. have a lower ion diffusion barrier than their resp. spinels. In this work, an attempt has been made to induce chem. pressure within the system by the use of a heavy cation, i.e., Sn4+ in the framework, to synthesize post-spinel NaMnSnO4 at ambient pressure conditions. The as-prepd. NaMnSnO4 samples are characterized with SEM, X-ray diffraction, inductively coupled plasma-at. emission spectroscopy and galvanostatic cycling with potential limitation measurements.
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  26. 26
    Ling, C.; Mizuno, F. Phase stability of post-spinel compound AMn2O4 (A = Li, Na, or Mg) and its application as a rechargeable battery cathode. Chem. Mater. 2013, 25, 3062– 3071,  DOI: 10.1021/cm401250c
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    26
    Phase stability of post-spinel compound AMn2O4 (A = Li, Na, or Mg) and its application as a rechargeable battery cathode
    Ling, Chen; Mizuno, Fuminori
    Chemistry of Materials (2013), 25 (15), 3062-3071CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    At high pressures, spinel compds. can transform to CaFe2O4, CaMn2O4, or CaTi2O4 phases, which are regarded as post-spinel phases. Here, first-principles calcns. are used to systematically study the stability of post-spinel LiMn2O4, NaMn2O4, and MgMn2O4, as well as their potential application as rechargeable battery cathodes. Thermodynamically, the stability of the post-spinel phase is highly related to the electronic configuration of transition-metal ions. By changing the concn. of Jahn-Teller active Mn3+, the relative stabilities of post-spinel phases can be easily monitored. It provides a practical way to obtain post-spinel compds. with desirable structures. Kinetically, post-spinel phases can be stable under ambient conditions, because of the high barrier that must be overcome to rearrange MnO6 octahedrons. The most spectacular finding in this work is the high cationic mobility in post-spinel compds. The activation energy barrier of the migration of Mg2+ in CaFe2O4-type MgMn2O4 is 0.4 eV, suggesting that the mobility of Mg2+ in this compd. is comparable to that of Li+ in typical Li-ion battery cathodes. To explore the potential application of post-spinel compds. as rechargeable battery cathodes, the voltage profile for the electrochem. insertion/removal of Mg in CaFe2O4-type MgMn2O4 is predicted. Its theor. energy d. is 1.3 times greater than that of typical Li-ion battery cathodes. These outstanding properties make CaFe2O4-type MgMn2O4 an attractive cathode candidate for rechargeable Mg batteries.
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  27. 27
    Hannah, D. C.; Sai Gautam, G.; Canepa, P.; Rong, Z.; Ceder, G. Magnesium ion mobility in post-spinels accessible at ambient pressure. Chem. Commun. 2017, 53, 5171– 5174,  DOI: 10.1039/C7CC01092C
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    27
    Magnesium ion mobility in post-spinels accessible at ambient pressure
    Hannah, Daniel C.; Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Rong, Ziqin; Ceder, Gerbrand
    Chemical Communications (Cambridge, United Kingdom) (2017), 53 (37), 5171-5174CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    We propose that Ti-contg. post-spinels may offer a practically-accessible route to fast multivalent ion diffusion in close-packed oxide lattices, with the caveat that substantial thermodn. driving forces for conversion reactions exist.
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  28. 28
    Dompablo, M. E. A.; Krich, C.; Nava-Avendaño, J.; Biškup, N.; Palacín, M. R.; Bardé, F. A joint computational and experimental evaluation of CaMn2O4 polymorphs as cathode materials for Ca ion batteries. Chem. Mater. 2016, 28, 6886– 6893,  DOI: 10.1021/acs.chemmater.6b02146
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    28
    A Joint Computational and Experimental Evaluation of CaMn2O4 Polymorphs as Cathode Materials for Ca Ion Batteries
    Dompablo, M. Elena Arroyo-de; Krich, Christopher; Nava-Avendano, Jessica; Biskup, Neven; Palacin, M. Rosa; Barde, Fanny
    Chemistry of Materials (2016), 28 (19), 6886-6893CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    The identification of potential cathode materials is a must for the development of a new calcium-ion based battery technol. In this work, we have first explored the electrochem. behavior of marokite-CaMn2O4 but the exptl. attempts to deinsert Ca ion from this compd. failed. First-principles calcns. indicate that in terms of voltage and capacity, marokite-CaMn2O4 could sustain reversible Ca deinsertion reactions; half decalciation is predicted at an av. voltage of 3.7 V with a vol. variation of 6%. However, the calcd. barriers for Ca diffusion are too high (1 eV), in agreement with the obsd. difficulty to deinsert Ca ion from the marokite structure. We have extended the computational investigation to two other CaMn2O4 polymorphs, the spinel and the CaFe2O4 structural types. Full Ca extn. from these CaMn2O4 polymorphs is predicted at an av. voltage of 3.1 V, but with a large vol. variation of around 20%. Structural factors limiting Ca diffusion in the three polymorphs are discussed and confronted with a previous computational investigation of the virtual-spinel [Ca]T[Mn2]OO4. Regardless the potential interest of [Ca]T[Mn2]OO4 as cathode for Ca ion batteries, calcns. suggests that the synthesis of this compd. would hardly be feasible. The present results unravel the bottlenecks assocd. with the design of feasible intercalation Ca electrode materials, and allow proposing guidelines for future research.
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  29. 29
    Müller-Buschbaum, H. The crystal chemistry of AM2O4 oxometallates. J. Alloys Compd. 2003, 349, 49– 104,  DOI: 10.1016/S0925-8388(02)00925-8
    Google Scholar
    29
    The crystal chemistry of AM2O4 oxometallates
    Muller-Buschbaum, Hk.
    Journal of Alloys and Compounds (2003), 349 (1-2), 49-104CODEN: JALCEU; ISSN:0925-8388. (Elsevier Science B.V.)
    This review summarizes the crystal chem. of oxometallates AM2O4, which indicates that >50 individual structure types regarding the formulas AM2O4 or A2MO4 exist. The spectrum of reported structures includes spinels, spineloids, compds. with closed and interrupted octahedra layers, tunnel structures, as well as square-planar polygons and dumb-bells. Irregular polyhedra around large metal ions were estd. by calcns. of effective coordination nos. (ECoN). Calcns. of the Coulomb terms of the lattice energy (MAPLE) lead to the centers of stereochem. active lone pairs in AM2O4 compds. contg. s2 cations. The positions of lone pairs and their crystal chem. function are pointed out in the corresponding figures.
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  30. 30
    Akimoto, J.; Takei, H. Synthesis and crystal structure of NaTi2O4: a new mixed-valence sodium titanate. J. Solid State Chem. 1989, 79, 212– 217,  DOI: 10.1016/0022-4596(89)90268-5
    Google Scholar
    30
    Synthesis and crystal structure of NaTi2O4: a new mixed-valence sodium titanate
    Akimoto, J.; Takei, H.
    Journal of Solid State Chemistry (1989), 79 (2), 212-17CODEN: JSSCBI; ISSN:0022-4596.
    Needle-shaped, black NaTi2O4, crystals, prepd. by the thermal reaction of Na2O with Ti2O3 and TiO2, crystallize in the orthorhombic Ca ferrite-type structure, space group Pnam with a 9.2615(10), b 10.7357(7), c 2.9556(3) Å, Z = 4, R = 0.029 and Rw = 0.034 for 1856 obsd. reflections. The framework structure is built up from double rutile chains, and 2 types of Ti sites are randomly occupied by Ti3+ and Ti4+ ions.
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  31. 31
    Darriet, J.; Vidal, A. Les composés NaRu2O4 et NaFeRuO4. Structure cristalline de NaFeRuO4. Bull. Soc. Fr. Minéral Cristallogr. 1975, 98, 374– 377
    Google Scholar
    31
    NaRu2O4 (sodium ruthenate) and NaFeRuO4 (sodium iron ruthenate) phases. Crystal structure of NaFeRuO4 (sodium iron ruthenate)
    Darriet, Jacques; Vidal, Alain
    Bulletin de la Societe Francaise de Mineralogie et de Cristallographie (1975), 98 (6), 374-7CODEN: BUFCAE; ISSN:0037-9328.
    NaRu2O4 and NaFeRuO4 crystd. in the orthorhombic system, isotypic with CaFe2O (NaRu2O4 a 9.265, b 2.821, c 11.159 Å; NaFeRuO4 a 9.218, b 2.956, c 10.848 Å). Single-crystal x-ray structure detn. of NaFeRuO4 shows that Fe and Ru atoms are randomly distributed between both independent crystallog. sites.
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  32. 32
    Viciu, L.; Ryser, A.; Mensing, C.; Bos, J.-W. G. Ambient-pressure synthesis of two new vanadium-based calcium ferrite-type compounds: NaV1.25Ti0.75O4 and NaVSnO4. Inorg. Chem. 2015, 54, 7264– 7271,  DOI: 10.1021/acs.inorgchem.5b00655
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    32
    Ambient-Pressure Synthesis of Two New Vanadium-Based Calcium Ferrite-Type Compounds: NaV1.25Ti0.75O4 and NaVSnO4
    Viciu, Liliana; Ryser, Alice; Mensing, Christian; Bos, Jan-Willem G.
    Inorganic Chemistry (2015), 54 (15), 7264-7271CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Two new CaFe2O4-type compds. NaV1.25Ti0.75O4 (1) and NaVSnO4 (2) were prepd. at ambient pressure and temps. < 800°. This contrasts with the parent material NaV2O4 which was synthesized at 6 GPa and 1300°. The lattice parameters are a 9.1500(4), b 2.9399(3), and c 10.6568(5) Å for 1 and a 9.3083(6), b 3.0708(2), and c 10.9194(5) Å for 2 (space group Pnma). Crystallog. data and at. coordinates are given. Structure refinement against neutron powder diffraction data reveals that V/Ti and V/Sn are disordered over two octahedral sites. Both materials were characterized by a magnetic transition near 150 K below which the Curie moment is reduced from a value consistent with V3+ [0.75 emu molV-1 K-1 for 1 and 0.58 emu molV-1 K-1 for 2] to 0.23 emu molV-1 K-1 for 1 and 0.30 emu molV-1 K-1 for 2, signaling a 70-50% redn. in the paramagnetic moment. The Weiss temp. (θ) is reduced from -285(1) and -138 K (2) to values close to 0 K, suggesting that the remaining spins are dil. and weakly interacting. Heat capacity measurements reveal a gradual loss of magnetic entropy between 2 and 150 K, consistent with short-range bulk magnetic ordering. Heat capacity and magnetic susceptibility measurements reveal a no. of weak magnetic transitions <6 K involving both antiferromagnetic and ferromagnetic components.
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  33. 33
    Akimoto, J.; Awaka, J.; Kijima, N.; Takahashi, Y.; Maruta, Y.; Tokiwa, K.; Watanabe, T. High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure. J. Solid State Chem. 2006, 179, 169– 174,  DOI: 10.1016/j.jssc.2005.10.020
    Google Scholar
    33
    High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure
    Akimoto, Junji; Awaka, Junji; Kijima, Norihito; Takahashi, Yasuhiko; Maruta, Yuichi; Tokiwa, Kazuyasu; Watanabe, Tsuneo
    Journal of Solid State Chemistry (2006), 179 (1), 169-174CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
    Single crystals of a new Na Mn oxide, NaMn2O4, were synthesized for the 1st time using a high-temp. and high-pressure technique. The NaMn2O4 single crystal is black, has a needle shape, and crystallizes in the orthorhombic Ca ferrite-type structure, space group Pnam with a 8.9055(18), b 11.0825(22), c 2.8524(5) Å, and Z = 4. The structure was detd. from a single-crystal x-ray study and refined to the conventional values R = 0.041 and Rw = 0.034 for 1190 obsd. reflections. Crystallog. data and at. coordinates are given. The framework structure is built up from edge-sharing chains of MnO6 octahedra that condense to form 1-dimensional tunnels in which the Na atoms are located. The Mn-O bond distance and bond valence analyses revealed the Mn valence Mn3+/Mn4+ ordering in the two double rutile chains of NaMn2O4.
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  34. 34
    Yamaura, K.; Huang, Q.; Moldovan, M.; Young, D. P.; Sato, A.; Baba, Y.; Nagai, T.; Matsui, Y.; Takayama-Muromachi, E. High-pressure synthesis, crystal structure determination, and a Ca substitutional study of the metallic rhodium oxide NaRh2O4. Chem. Mater. 2005, 17, 359– 365,  DOI: 10.1021/cm0483846
    Google Scholar
    34
    High-Pressure Synthesis, Crystal Structure Determination, and a Ca Substitution Study of the Metallic Rhodium Oxide NaRh2O4
    Yamaura, Kazunari; Huang, Qingzhen; Moldovan, Monica; Young, David P.; Sato, Akira; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Takayama-Muromachi, Eiji
    Chemistry of Materials (2005), 17 (2), 359-365CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    The sodium rhodate NaRh2O4 was synthesized for the first time and characterized by neutron and x-ray diffraction studies and measurements of magnetic susceptibility, sp. heat, elec. resistivity, and the Seebeck coeff. NaRh2O4 crystallizes in the CaFe2O4-type structure, which is comprised of a characteristic RhO6 octahedral network. The compd. is metallic in nature, probably reflecting the 1:1 mixed valence character of Rh(III) and Rh(IV) in the network. For further studies of the compd., the Rh valence was varied significantly by an aliovalent substitution: the full-range solid soln. between NaRh2O4 and CaRh2O4 was achieved and characterized as well. The metallic state was dramatically altered, and a peculiar magnetism developed in the low Na concn. range.
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  35. 35
    Shukaev, I. L.; Volochaev, V. A. Ternary sodium and titanium oxides with cobalt(II). Russ. J. Inorg. Chem. 1995, 12, 1974– 1980
    Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Nalbandyan, V. B.; Shukaev, I. L. Triple oxides of sodium, nickel, and titanium. Russ. J. Inorg. Chem. 1992, 37, 1231– 1235
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Archaimbault, F.; Choisnet, J.; Rautureau, M. New ferriantimonates with the CaFe2O4 type structure: Na2Fe3SbO8 and isomorphous series Na2Fe2+xSn2–2xSbxO8 (0 ≤ x ≤ 1). Eur. J. Solid State Inorg. Chem. 1988, 25, 573– 587
    Google Scholar
    There is no corresponding record for this reference.
  38. 38
    Ishiguro, T.; Tanaka, K.; Marumo, F.; Ismail, M. G. M. U.; Hirano, S.; Somiya, S. Non-stoichiometric sodium iron (II) titanium (IV) oxide. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1978, 34, 3346– 3348,  DOI: 10.1107/S0567740878010870
    Google Scholar
    There is no corresponding record for this reference.
  39. 39
    Feger, C. R.; Kolis, J. W. Na3Mn4Te2O12. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1998, 54, 1055– 1057,  DOI: 10.1107/S0108270197020076
    Google Scholar
    39
    Na3Mn4Te2O12
    Feger, Christopher R.; Kolis, Joseph W.
    Acta Crystallographica, Section C: Crystal Structure Communications (1998), C54 (8), 1055-1057CODEN: ACSCEE; ISSN:0108-2701. (Munksgaard International Publishers Ltd.)
    The title compd., Na Mn tellurate, was obtained by hydrothermal synthesis and adopts a super-structure related to the CaFe2O4 structure type, with the Mn and Te atoms ordered along the b axis (short axis in the CaFe2O4 structure). Electron-counting schemes show that this compd. is a mixed-valence MnII/MnIII compd., and bond valence sums were used to suggest that there is no site preference for the higher charged Mn atom. Crystallog. data are given.
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  40. 40
    Toby, B. H.; Von Dreele, R. B. GSAS-II: the genesis of a modern open-source all purpose crystallography software package. J. Appl. Crystallogr. 2013, 46, 544– 549,  DOI: 10.1107/S0021889813003531
    Google Scholar
    40
    GSAS-II: the genesis of a modern open-source all purpose crystallography software package
    Toby, Brian H.; Von Dreele, Robert B.
    Journal of Applied Crystallography (2013), 46 (2), 544-549CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
    The newly developed GSAS-II software is a general purpose package for data redn., structure soln. and structure refinement that can be used with both single-crystal and powder diffraction data from both neutron and x-ray sources, including lab. and synchrotron sources, collected on both two- and 1-dimensional detectors. It is intended that GSAS-II will eventually replace both the GSAS and the EXPGUI packages, as well as many other utilities. GSAS-II is open source and is written largely in object-oriented Python but offers speeds comparable to compiled code because of its reliance on the Python NumPy and SciPy packages for computation. It runs on all common computer platforms and offers highly integrated graphics, both for a user interface and for interpretation of parameters. The package can be applied to all stages of crystallog. anal. for const.-wavelength x-ray and neutron data. Plans for considerable addnl. development are discussed.
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  41. 41
    Amoureux, J.-P.; Fernandez, C.; Steuernagel, S. Z Filtering in MQMAS NMR. J. Magn. Reson., Ser. A 1996, 123, 116– 118,  DOI: 10.1006/jmra.1996.0221
    Google Scholar
    41
    Z filtering in MQMAS NMR
    Amoureux, Jean-Paul; Fernandez, Christian; Steuernageel, Stefan
    Journal of Magnetic Resonance, Series A (1996), 123 (1), 116-118CODEN: JMRAE2; ISSN:1064-1858. (Academic)
    A Z-filtering method is applied to MQMAS NMR which greatly improves the efficiency of the method. This approach was used to analyze the 27Al 3QMAS NMR spectrum of AlPO-14.
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  42. 42
    Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
    Google Scholar
    42
    Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
    Kresse, G.; Furthmuller, J.
    Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
    The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
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  43. 43
    Kresse, G.; Hafner, J. Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements. J. Phys.: Condens. Matter 1994, 6, 8245,  DOI: 10.1088/0953-8984/6/40/015
    Google Scholar
    43
    Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements
    Kresse, G.; Hafner, J.
    Journal of Physics: Condensed Matter (1994), 6 (40), 8245-57CODEN: JCOMEL; ISSN:0953-8984.
    The construction of accurate pseudopotentials with good convergence properties for the first-row and transition elements is discussed. By combining an improved description of the pseudo-wavefunction inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence can be achieved. With the new pseudopotentials, basis sets with no more than 75-100 plane waves per atom are sufficient to reproduce the results obtained with the most accurate norm-conserving pseudopotentials.
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  44. 44
    Blöchl, P. E.; Jepsen, O.; Andersen, O. K. Improved tetrahedron method for Brillouin-zone integrations. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 49, 16223,  DOI: 10.1103/PhysRevB.49.16223
    Google Scholar
    44
    Improved tetrahedron method for Brillouin-zone integrations
    Blochl, Peter E.; Jepsen, O.; Andersen, O. K.
    Physical Review B: Condensed Matter and Materials Physics (1994), 49 (23), 16223-33CODEN: PRBMDO; ISSN:0163-1829.
    Several improvements of the tetrahedron method for Brillouin-zone integrations are presented. (1) A translational grid of k points and tetrahedra is suggested that renders the results for insulators identical to those obtained with special-point methods with the same no. of k points. (2) A simple correction formula goes beyond the linear approxn. of matrix elements within the tetrahedra and also improves the results for metals significantly. For a required accuracy this reduces the no. of k points by orders of magnitude. (3) Irreducible k points and tetrahedra are selected by a fully automated procedure, requiring as input only the space-group operations. (4) The integration is formulated as a weighted sum over irreducible k points with integration wts. calcd. using the tetrahedron method once for a given band structure. This allows an efficient use of the tetrahedron method also in plane-wave-based electronic-structure methods.
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  45. 45
    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
    Google Scholar
    45
    Generalized gradient approximation made simple
    Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
    Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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  46. 46
    Wang, L.; Maxisch, T.; Ceder, G. Oxidation energies of transition metal oxides within the GGA+U framework. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 195107,  DOI: 10.1103/PhysRevB.73.195107
    Google Scholar
    46
    Oxidation energies of transition metal oxides within the GGA+U framework
    Wang, Lei; Maxisch, Thomas; Ceder, Gerbrand
    Physical Review B: Condensed Matter and Materials Physics (2006), 73 (19), 195107/1-195107/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    The energy of a large no. of oxidn. reactions of 3d transition metal oxides is computed using the generalized gradient approach (GGA) and GGA+U methods. Two substantial contributions to the error in GGA oxidn. energies are identified. The first contribution originates from the overbinding of GGA in the O2 mol. and only occurs when the oxidant is O2. The second error occurs in all oxidn. reactions and is related to the correlation error in 3d orbitals in GGA. Strong self-interaction in GGA systematically penalizes a reduced state (with more d electrons) over an oxidized state, resulting in an overestimation of oxidn. energies. The const. error in the oxidn. energy from the O2 binding error can be cor. by fitting the formation enthalpy of simple nontransition metal oxides. Removal of the O2 binding error makes it possible to address the correlation effects in 3d transition metal oxides with the GGA+U method. Calcd. oxidn. energies agree well with exptl. data for reasonable and consistent values of U.
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  47. 47
    Jain, A.; Ong, S. P.; Hautier, G.; Chen, W.; Richards, W. D.; Dacek, S.; Cholia, S.; Gunter, D.; Skinner, D.; Ceder, G.; Persson, K. A. Commentary: The Materials Project: A materials genome approach to accelerating materials innovation. APL Mater. 2013, 1, 011002,  DOI: 10.1063/1.4812323
    Google Scholar
    47
    Commentary: The Materials Project: A materials genome approach to accelerating materials innovation
    Jain, Anubhav; Ong, Shyue Ping; Hautier, Geoffroy; Chen, Wei; Richards, William Davidson; Dacek, Stephen; Cholia, Shreyas; Gunter, Dan; Skinner, David; Ceder, Gerbrand; Persson, Kristin A.
    APL Materials (2013), 1 (1), 011002/1-011002/11CODEN: AMPADS; ISSN:2166-532X. (American Institute of Physics)
    Accelerating the discovery of advanced materials is essential for human welfare and sustainable, clean energy. In this paper, we introduce the Materials Project (www.materialsproject.org), a core program of the Materials Genome Initiative that uses high-throughput computing to uncover the properties of all known inorg. materials. This open dataset can be accessed through multiple channels for both interactive exploration and data mining. The Materials Project also seeks to create open-source platforms for developing robust, sophisticated materials analyses. Future efforts will enable users to perform rapid-prototyping'' of new materials in silico, and provide researchers with new avenues for cost-effective, data-driven materials design. (c) 2013 American Institute of Physics.
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  48. 48
    Jain, A.; Hautier, G.; Ong, S. P.; Moore, C. J.; Fischer, C. C.; Persson, K. A.; Ceder, G. Formation enthalpies by mixing GGA and GGA + U calculations. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 84, 045115,  DOI: 10.1103/PhysRevB.84.045115
    Google Scholar
    48
    Formation enthalpies by mixing GGA and GGA + U calculations
    Jain, Anubhav; Hautier, Geoffroy; Ong, Shyue Ping; Moore, Charles J.; Fischer, Christopher C.; Persson, Kristin A.; Ceder, Gerbrand
    Physical Review B: Condensed Matter and Materials Physics (2011), 84 (4), 045115/1-045115/10CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    Std. approxns. to the d. functional theory exchange-correlation functional have been extraordinarily successful, but calcg. formation enthalpies of reactions involving compds. with both localized and delocalized electronic states remains challenging. In this work the authors examine the shortcomings of the generalized gradient approxn. (GGA) and GGA + U in accurately characterizing such difficult reactions. They then outline a methodol. that mixes GGA and GGA + U total energies (using known binary formation data for calibration) to more accurately predict formation enthalpies. For a test set of 49 ternary oxides, this methodol. can reduce the mean abs. relative error in calcd. formation enthalpies from approx. 7.7-21% in GGA + U to under 2%. As another example, the authors show that neither GGA nor GGA + U alone accurately reproduces the Fe-P-O phase diagram; however, the mixed methodol. successfully predicts all known phases as stable by naturally stitching together GGA and GGA + U results. As a final example, this technique was applied to the calcn. of the Li-conversion voltage of LiFeF3. These results indicate that mixing energies of several functionals represents one avenue to improve the accuracy of total energy computations without affecting the cost of calcn.
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  49. 49
    Ong, S. P.; Richards, W. D.; Jain, A.; Hautier, G.; Kocher, M.; Cholia, S.; Gunter, D.; Chevrier, V. L.; Persson, K. A.; Ceder, G. Python Materials Genomics (pymatgen): A robust, open-source python library for materials analysis. Comput. Mater. Sci. 2013, 68, 314– 319,  DOI: 10.1016/j.commatsci.2012.10.028
    Google Scholar
    49
    Python Materials Genomics (pymatgen): A robust, open-source python library for materials analysis
    Ong, Shyue Ping; Richards, William Davidson; Jain, Anubhav; Hautier, Geoffroy; Kocher, Michael; Cholia, Shreyas; Gunter, Dan; Chevrier, Vincent L.; Persson, Kristin A.; Ceder, Gerbrand
    Computational Materials Science (2013), 68 (), 314-319CODEN: CMMSEM; ISSN:0927-0256. (Elsevier B.V.)
    We present the Python Materials Genomics (pymatgen) library, a robust, open-source Python library for materials anal. A key enabler in high-throughput computational materials science efforts is a robust set of software tools to perform initial setup for the calcns. (e.g., generation of structures and necessary input files) and post-calcn. anal. to derive useful material properties from raw calcd. data. The pymatgen library aims to meet these needs by (1) defining core Python objects for materials data representation, (2) providing a well-tested set of structure and thermodn. analyses relevant to many applications, and (3) establishing an open platform for researchers to collaboratively develop sophisticated analyses of materials data obtained both from first principles calcns. and expts. The pymatgen library also provides convenient tools to obtain useful materials data via the Materials Project's REpresentational State Transfer (REST) Application Programming Interface (API). As an example, using pymatgen's interface to the Materials Project's RESTful API and phase diagram package, we demonstrate how the phase and electrochem. stability of a recently synthesized material, Li4SnS4, can be analyzed using a min. of computing resources. We find that Li4SnS4 is a stable phase in the Li-Sn-S phase diagram (consistent with the fact that it can be synthesized), but the narrow range of lithium chem. potentials for which it is predicted to be stable would suggest that it is not intrinsically stable against typical electrodes used in lithium-ion batteries.
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  50. 50
    Avdeev, M. Yu; Nalbandyan, V. B.; Medvedev, B. S. Hexagonal sodium titanate chromite: a new high-conductivity solid electrolyte. Inorg. Mater. 1997, 33, 500– 503
    Google Scholar
    50
    Hexagonal sodium titanate chromite: a new high-conductivity solid electrolyte
    Avdeev, M. Yu.; Nalbandyan, V. B.; Medvedev, B. S.
    Inorganic Materials (Translation of Neorganicheskie Materialy) (1997), 33 (5), 500-503CODEN: INOMAF; ISSN:0020-1685. (MAIK Nauka/Interperiodica)
    NaxCrxTi1-xO2, a new nonstoichiometric hexagonal layered phase with high sodium ion cond., was prepd. by solid-state reaction in a controlled atm. Its stability field was outlined, the lattice parameters calcd., and the crystal chem. of cation cond. was discussed.
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  51. 51
    Mumme, W. G.; Reid, A. F. Non-stoichiometric sodium iron titanate, NaxFexTi2-xO4, 0.90> x> 0.75. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1968, 24, 625– 631,  DOI: 10.1107/S0567740868002955
    Google Scholar
    51
    Non-stoichiometric sodium iron titanate, Na(sub x)Fe(sub x)Ti(sub 2-x)O4, 0.90>x>0.75
    Mumme, W. G.; Reid, A. F.
    Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1968), 24 (Pt. 5), 625-31CODEN: ACBCAR; ISSN:0567-7408.
    The new, congruently melting compd. NaxFexTi2-xO4, 0.90 > x > 0.75, was prepd. as a powder at 1000° and in the cryst. form by melting NaFeTiO4 in air at 1220°. It is orthorhombic, space group Pnma, with unit-cell dimensions a 9.248, b 2.973, and c 11.344 A. at the compn. x = 0.90. The Fe and Ti atoms randomly occupy octahedral positions, and the octahedra within a unit cell are joined by extensive edge-sharing into Z-shaped groups of 4. These groups extend in infinite ribbons in the b-axis direction, and are corner joined to each other, thereby providing double tunnels of Na-ion sites, not all occupied. The structure is a rearrangement, with a necessary Na loss, of the limiting compn. NaFeTiO4, which is a CaFe2O4 isotype with similar crystallographic consts., but contg. pairs of edge-shared octahedra corner joined to form single tunnels for Na ions.
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  52. 52
    Nalbandyan, V. B.; Rykalova, S. I.; Bikyashev, E. A.; Isakova, S. Yu Sodium titanium magnesium (zinc) ternary oxides. Zh. Neorg. Khim. 1989, 34, 2381– 2386
    Google Scholar
    52
    Ternary oxides of sodium, titanium and magnesium or zinc
    Nalbandyan, V. B.; Rykalova, S. I.; Bikyashev, E. A.; Isakova, S. Yu.
    Zhurnal Neorganicheskoi Khimii (1989), 34 (9), 2381-6CODEN: ZNOKAQ; ISSN:0044-457X.
    Subsolidus phase equil. was studied in the Na8Ti5O14-TiO2-ZnO(MgO) systems at 900-1100°. Crystn. from melts or from molten NaF was studied for MgO compns. Ten ternary oxides and 1 oxyfluoride were identified. Their structures are related to NaTi-bronzes, nonstoichiometric Na ferrititanate, α-NaFeO2, Na4Ti5O12, and 4 new structure types. The crystallochem. of these compds. is discussed.
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  53. 53
    Shukaev, I. L.; Butova, V. V.; Chernenko, S. V.; Pospelov, A. A.; Shapovalov, V. V.; Guda, A. A.; Aboraia, A. M.; Zahran, H. Y.; Yahia, I. S.; Soldatov, A. V. New orthorhombic sodium iron(+2) titanate. Ceram. Int. 2020, 46, 4416– 4422,  DOI: 10.1016/j.ceramint.2019.10.167
    Google Scholar
    53
    New orthorhombic sodium iron(+2) titanate
    Shukaev, Igor L.; Butova, Vera V.; Chernenko, Sergey V.; Pospelov, Andrey A.; Shapovalov, Victor V.; Guda, Alexander A.; Aboraia, Abdelaziz M.; Zahran, Heba Y.; Yahia, Ibrahim S.; Soldatov, Alexander V.
    Ceramics International (2020), 46 (4), 4416-4422CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
    The set of compns. with Fe2+ in the system NaxFex/2Ti2-x/2O4 has been prepd. by solid-state reactions in the inert atm. at 1050 °C. The oxidn. state of iron was confirmed using the XANES method. Na0.88Fe0.44Ti1.56O4 is the new four-element compd. in Na2O-"FeO"-TiO2 system. According to the X-ray powder data, it is orthorhombic, Pnma, a = 9.3624(1), b = 2.96718(4), c = 11.3435(1) Å and has the same structure as Na0.9Fe0.9Ti1.1O4 with Fe3+. The structure was refined by the Rietveld method. The 3D-framework of (Fe, Ti)O6 octahedra contains quadruple rutile-like chains and sodium ions in double tunnels. Fe/Ti partial ordering in the framework and sodium distribution in the tunnels were studied addnl. using the method of bond valence sums and Voronoi tessellation. The structure and compn. of Na0.88Fe0.44Ti1.56O4 make it a promising material for cathode application.
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  54. 54
    Thackeray, M. M.; de Kock, A.; Rossouw, M. H.; Liles, D.; Bittihn, R.; Hoge, D. Spinel electrodes from the Li-Mn-O system for rechargeable lithium battery applications. J. Electrochem. Soc. 1992, 139, 363– 366,  DOI: 10.1149/1.2069222
    Google Scholar
    54
    Spinel electrodes from the lithium-manganese-oxygen system for rechargeable lithium battery applications
    Thackeray, M. M.; De Kock, A.; Rossouw, M. H.; Liles, D.; Bittihn, R.; Hoge, D.
    Journal of the Electrochemical Society (1992), 139 (2), 363-6CODEN: JESOAN; ISSN:0013-4651.
    The electrochem. and structural properties of spinel phases in the Li-Mn-O system are discussed as insertion electrodes for rechargeable lithium batteries. The performance of button-type cells contg. electrodes from the Li2O yMnO2 system, e.g., the stoichiometric spinel Li4Mn5O12 (y = 2.5) and the defect spinel Li2Mn4O9 (y = 4.0), is highlighted and compared with a cell contg. a std. LiMn2O4 spinel electrode.
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  55. 55
    Deschanvres, A.; Raveau, B.; Sekkal, Z. Mise en evidence et etude cristallographique d’une nouvelle solution solide de type spinelle Li1+xTi2–xO4 0 ⩽ x ⩽ 0, 333. Mater. Res. Bull. 1971, 6, 699– 704,  DOI: 10.1016/0025-5408(71)90103-6
    Google Scholar
    55
    Demonstration and crystallographic study of new spinel-type solid solution Li1+xTi1-3xTi1+2xO4 with O .leq. .tim. .leq. 0.33
    Deschanvres, A.; Raveau, B.; Sekkal, Z.
    Materials Research Bulletin (1971), 6 (8), 699-704CODEN: MRBUAC; ISSN:0025-5408.
    A new solid-soln. spinel type Li1+xTi3+1-3x-Ti4+1+2xO4 with O ≤ x ≤ 0.33 has been isolated. The positions of the different atoms in the cubic cell were detd.
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  56. 56
    Rickert, K.; Sedefoglu, N.; Malo, S.; Caignaert, V.; Kavak, H.; Poeppelmeier, K. R. Structural, electrical, and optical properties of the tetragonal, fluorite-related Zn0.456In1.084Ge0.460O3. Chem. Mater. 2015, 27, 5072– 5079,  DOI: 10.1021/acs.chemmater.5b01724
    Google Scholar
    56
    Structural, Electrical, and Optical Properties of the Tetragonal, Fluorite-Related Zn0.456In1.084Ge0.460O3
    Rickert, Karl; Sedefoglu, Nazmi; Malo, Sylvie; Caignaert, Vincent; Kavak, Hamide; Poeppelmeier, Kenneth R.
    Chemistry of Materials (2015), 27 (14), 5072-5079CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    We report the discovery of Zn0.456In1.084Ge0.460O3, a material closely related to bixbyite. In contrast, however, the oxygen atoms in this new phase occupy 4 Wyckoff positions, which result in 4 four-coordinate, 24 six-coordinate (2 different Wyckoff positions), and 4 eight-coordinate sites as compared to the 32 six-coordinate (also 2 different Wyckoff positions) sites of bixbyite. This highly ordered material is related to fluorite, Ag6GeSO8, and γ-UO3 and is n-type with a bulk carrier concn. of 4.772 × 1014 cm-3. The reduced form displays an av. room temp. cond. of 99(11) S·cm-1 and an av. optical band gap of 2.88(1) eV. These properties are comparable to those of In2O3, which is the host material for the current leading transparent conducting oxides. The structure of Zn0.456In1.084Ge0.460O3 is solved from a combined refinement of synchrotron X-ray powder diffraction and time-of-flight neutron powder diffraction and confirmed with electron diffraction. The soln. is a new, layered, tetragonal structure in the I41/amd space group with a = 7.033986(19) Å and c = 19.74961(8) Å. The complex cationic topol. network adopted by Zn0.456In1.084Ge0.460O3 offers the potential for future studies to further understand carrier generation in ∼3 eV oxide semiconductors.
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  57. 57
    Marinkovic, B. A.; Mancic, L.; Jardim, P. M.; Milosevic, O.; Rizzo, F. Hydrothermal synthesis of NaxFexTi2-xO4 from natural ilmenite sand: a CaFe2O4 structure type compound. Solid State Commun. 2008, 145, 346– 350,  DOI: 10.1016/j.ssc.2007.12.006
    Google Scholar
    57
    Hydrothermal synthesis of NaxFexTi2-xO4 from natural ilmenite sand: A CaFe2O4 structure type compound
    Marinkovic, B. A.; Mancic, L.; Jardim, P. M.; Milosevic, O.; Rizzo, F.
    Solid State Communications (2008), 145 (7-8), 346-350CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)
    NaxFexTi2-xO4, a compd. with CaFe2O4-type structure, was obtained via hydrothermal route at <200°C. Natural ilmenite sand, a low cost reagent, was used as a precursor and reacted with 10 mol/L NaOH for 70 h to obtained high yield (92% wt) of NaxFexTi2-xO4 with x = 0.76-0.79 , as evaluated through the Rietveld refinement and quant. phase anal. of X-ray powder diffraction data. TEM showed that NaxFexTi2-xO4 appears in submicron to micron crystals with well-defined facets, growing along the [001] crystallog. direction, which means that the tunnels, a peculiarity of this crystal structure, are oriented along the direction of growth.
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  58. 58
    Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751– 767,  DOI: 10.1107/S0567739476001551
    Google Scholar
    There is no corresponding record for this reference.
  59. 59
    Mumme, W. G. The structure of Na4Mn4Ti5O18. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1968, 24, 1114– 1120,  DOI: 10.1107/S0567740868003778
    Google Scholar
    59
    Structure of Na4Mn4Ti5O18
    Mumme, W. G.
    Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1968), 24 (Pt. 8), 1114-20CODEN: ACBCAR; ISSN:0567-7408.
    Na4Mn4Ti5O18, formed at 1200° by crystn. from the compn. NaMnTiO4, is orthorhombic, with unit-cell dimensions a 9.268, b 26.601, c 2.888 A. Mn3+ and Ti4+ atoms occupy octahedral positions, while the coordination of another Mn3+ is a rectangular pyramid. In this structure, groups of octahedra, joined by extensive edge and corner sharing, are linked together by the 5-coordinated Mn3+ to leave a series of tunnels for the Na ions. One of these is a single tunnel similar to that found in Ca ferrite; the other is a much larger one and contains sites for 4 Na ions, only half of which are filled. The chem. compn. was deduced from this structure anal.
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  60. 60
    Parant, J.-P.; Olazcuaga, R.; Devalette, M.; Fouassier, C.; Hagenmuller, P. Sur quelques nouvelles phases de formule NaxMnO2 (x ≤ 1). J. Solid State Chem. 1971, 3, 1– 11,  DOI: 10.1016/0022-4596(71)90001-6
    Google Scholar
    60
    New phases of the formula NaxMnO2(x.leq.1)
    Parant, Jean P.; Olazcuaga, Roger; Devalette, Michel; Fouassier, Claude; Hagenmuller, Paul
    Journal of Solid State Chemistry (1971), 3 (1), 1-11CODEN: JSSCBI; ISSN:0022-4596.
    Several new ternary oxides have been isolated in the Mn-O-Na system for Na/Mn ≤ 1: Na0.20MnO2, Na0.40-MnO2, Na0.44MnO2, Na0.70MnO2+y(0 ≤ y ≤ 0.25), and NaMnO2. All structures are characterized by edge sharing (MnO6) octahedra, forming double or triple chains for small Na contents and 2-dimensional layers when the Na/Mn ratio becomes close to 1. Elec. and magnetic behavior of the phases has been detd.
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  61. 61
    Toda, K.; Kameo, Y.; Kurita, S.; Sato, M. Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO4 (Ln = rare earth). J. Alloys Compd. 1996, 234, 19– 25,  DOI: 10.1016/0925-8388(95)01969-3
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    61
    Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO4 (Ln = rare earth)
    Toda, Kenji; Kameo, Yutaka; Kurita, Satoru; Sato, Mineo
    Journal of Alloys and Compounds (1996), 234 (1), 19-25CODEN: JALCEU; ISSN:0925-8388. (Elsevier)
    The layered perovskite compds. NaLnTiO4 (Ln = rare earth element; LaNaTiO4, PrNaTiO4, NdNaTiO4, SmNaTiO4, EuNaTiO4, GdNaTiO4, YNaTiO4 and LuNaTiO4) were synthesized by the solid state reaction. The crystal structure of these compds. were detd. by the Rietveld anal. Single phases of the compds. (except for Ln = Lu) could be prepd. only under very restricted prepn. conditions. The compn. of NaLuTiO4 was not a single phase under the conditions employed in this study. Compds. NaLnTiO4 have a tetragonal symmetry for Ln = La-Nd, while an orthorhombic symmetry is obsd. for Ln = Sm-Lu. The stabilization of NaLnTiO4 is discussed on the basis of the relative sizes of the rare earth and the alkali metal ions. The lowering of the symmetry is considered to be introduced by the mismatch between TiO2 and LnO2 layers. Ionic conductivities attributed to the interlayer sodium ions were obsd. at high temps. The magnitude of ionic cond. of NaLaTiO4, with a single perovskite layer, was much higher than that of Na2La2Ti3O10, with a triple perovskite layer. This high ionic cond. is due to the weak interaction between the perovskite layer and interlayer sodium ions.
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  62. 62
    Bruhn, G.; Beutel, S.; Pfaff, G.; Albert, B. Low-temperature synthesis of freudenbergite-type titanate bronzes from metal halides, crystal growth from molybdate flux, and crystal structure determination of Na1.84Zn0.92Ti7.08O16. J. Alloys Compd. 2015, 644, 783– 787,  DOI: 10.1016/j.jallcom.2015.05.076
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    62
    Low-temperature synthesis of freudenbergite-type titanate bronzes from metal halides, crystal growth from molybdate flux, and crystal structure determination of Na1.84Zn0.92Ti7.08O16
    Bruhn, Gerd; Beutel, Sebastian; Pfaff, Gerhard; Albert, Barbara
    Journal of Alloys and Compounds (2015), 644 (), 783-787CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    A new pptn. method to synthesize freudenbergite-type phases from metal halides was developed, and titanate bronzes NaxMyTi8-yO16 with M = Fe, Zn were obtained as micro-cryst. powders. The crystal structures were refined based on synchrotron x-ray data using the Rietveld method. Single crystals of the new compd. Na1.848(8)Zn0.924(3)Ti7.076(3)O16 were grown from molybdate flux, and its crystal structure was detd. (space group C2/m, a 1230.2(2), b 381.94(4), c 650.2(2) pm, and β 107.09(2)°). Crystallog. data and at. coordinates are given. It is isostructural to the Fe-contg. freudenbergite-type phase. Absorption spectra from diffuse reflection measurements are shown.
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  63. 63
    Kunz, M.; Brown, I. D. Out-of-center distortions around octahedrally coordinated d0 transition metals. J. Solid State Chem. 1995, 115, 395– 406,  DOI: 10.1006/jssc.1995.1150
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    63
    Out-of-center distortions around octahedrally coordinated d0 transition metals
    Kunz, Martin; Brown, I. David
    Journal of Solid State Chemistry (1995), 115 (2), 395-406CODEN: JSSCBI; ISSN:0022-4596. (Academic)
    The bond valence growth approach was used to model the characteristic out-of-center electronic distortions around d0 transition model cations in octahedral coordination. The distortions are influenced not only by the electronic structure of the cation but also by the structure of the bond network, by lattice incommensurations, and by cation-cation repulsion. These latter effects often det. whether a distortion will occur and, if so, in what direction. Once the direction of an expected out-of-center distortion is known, its magnitude can be modeled using modified bond valence network equations, where certain bonds are weighted to take into account the intrinsic inequality of the bonds in such a distorted coordination. The arguments are illustrated by examples.
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  64. 64
    Ok, K. M.; Halasyamani, P. S.; Casanova, D.; Llunell, M.; Alemany, P.; Alvarez, S. Distortions in octahedrally coordinated d0 transition metal oxides: a continuous symmetry measures approach. Chem. Mater. 2006, 18, 3176– 3183,  DOI: 10.1021/cm0604817
    Google Scholar
    64
    Distortions in Octahedrally Coordinated d0 Transition Metal Oxides: A Continuous Symmetry Measures Approach
    Ok, Kang Min; Halasyamani, P. Shiv; Casanova, David; Llunell, Miquel; Alemany, Pere; Alvarez, Santiago
    Chemistry of Materials (2006), 18 (14), 3176-3183CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    More than 750 d0 transition metal oxide octahedra were examd. to better understand the out-of-center distortion occurring with these cations. A continuous symmetry measures approach was used to quantify the magnitude and direction of the distortion. Using this approach the authors were able to divide the d0 transition metals into three categories: strong (Mo6+ and V5+), moderate (W6+, Ti4+, Nb5+, and Ta5+), and weak (Zr4+ and Hf4+) distorters. The authors also examd. and discussed the directional preference of the distortion for each cation.
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  65. 65
    Urban, A.; Abdellahi, A.; Dacek, S.; Artrith, N.; Ceder, G. Electronic-structure origin of cation disorder in transition-metal oxides. Phys. Rev. Lett. 2017, 119, 176402,  DOI: 10.1103/PhysRevLett.119.176402
    Google Scholar
    65
    Electronic-structure origin of cation disorder in transition-metal oxides
    Urban, Alexander; Abdellahi, Aziz; Dacek, Stephen; Artrith, Nongnuch; Ceder, Gerbrand
    Physical Review Letters (2017), 119 (17), 176402/1-176402/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
    Cation disorder is an important design criterion for technol. relevant transition-metal (TM) oxides, such as radiation-tolerant ceramics and Li-ion battery electrodes. In this Letter, we use a combination of first-principles calcns., normal mode anal., and band-structure arguments to pinpoint a specific electronic-structure effect that influences the stability of disordered phases. We find that the electronic configuration of a TM ion dets. to what extent the structural energy is affected by site distortions. This mechanism explains the stability of disordered phases with large ionic radius differences and provides a concrete guideline for the discovery of novel disordered compns.
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  66. 66
    Shilov, G. V.; Atovmyan, L. O.; Volochaev, V. A.; Nalbandyan, V. B. Crystal structure and ionic conductivity of a new sodium magnesium titanium oxide. Kristallografiya 1999, 44, 1029– 1033
    Google Scholar
    66
    Crystal structure and ionic conductivity of a new sodium magnesium titanium oxide
    Shilov, G. V.; Atovmyan, L. O.; Volochaev, V. A.; Nalbandyan, V. B.
    Kristallografiya (1999), 44 (6), 1029-1033CODEN: KRISAJ; ISSN:0023-4761. (MAIK Nauka/Interperiodica Publishing)
    By solid-phase synthesis and crystn. from the melt a nonstoichiometric phase Na4+2x(MgxTi8-x)O18 (x = 0.76) was obtained. Crystals are monoclinic, space group B2/m, with a 23.063(8), b 10.689(4), c 2.944(2) Å , and γ 76.40(4)°; Z = 2; R = 0.0506 for 2679 reflections. At. coordinates are given. The framework from octahedra, statistically occupied by Mg and Ti atoms, contains one-dimensional 3-tube channels along the c-axis, in which occur the mobile Na ions. One of the tubes is occupied totally, the other two partially, with splitting of position, guaranteeing dispersal of Na+. Passage between positions is tighter, than in related structures, consequently the ionic cond. of the ceramic is lower: 2 × 10-3 S/m at 300°.
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  67. 67
    Ishiguro, T.; Tanaka, K.; Marumo, F.; Ismail, M. G. M. U.; Hirano, S.; Somiya, S. Freudenbergite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1978, 34, 255– 256,  DOI: 10.1107/S0567740878002708
    Google Scholar
    There is no corresponding record for this reference.
  68. 68
    Pospelov, A. A.; Nalbandyan, V. B. Preparation, crystal structures and rapid hydration of P2- and P3-type sodium chromium antimony oxides. J. Solid State Chem. 2011, 184, 1043– 1047,  DOI: 10.1016/j.jssc.2011.03.011
    Google Scholar
    68
    Preparation, crystal structures and rapid hydration of P2- and P3-type sodium chromium antimony oxides
    Pospelov, A. A.; Nalbandyan, V. B.
    Journal of Solid State Chemistry (2011), 184 (5), 1043-1047CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
    Two new Nax[Cr(1+x)/2Sb(1-x)/2]O2 compds. were prepd. by solid-state reactions in Ar. Their structures were detd. by the x-ray Rietveld method. Both new phases together with NaCrO2-based solid soln. comprise brucite-like layers of edge-shared (Cr,Sb)O6 octahedra, but differ by packing mode of the layers and coordination of the interlayer Na+ ions. A P3 phase exists at x ≈ 0.5-0.58. It is rhombohedral (R3‾m), a 2.966, c 16.937 Å at x ≈ 0.58, with 29% Na+ occupancy of trigonal prisms. A P2 phase exists at x ≈ 0.6-0.7. It is hexagonal (P63/mmc), a 2.960, c 11.190 Å at x ≈ 0.7, with 37% and 33% Na+ occupancy of two nonequiv. trigonal prisms. Both P2 and P3 phases rapidly absorb moisture in air; packing mode is preserved, the a parameter changes slightly, but c increases by 24-25%. Very high Na ion cond. is predicted for both P2 and P3 anhyd. phases.
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  69. 69
    Politaev, V. V.; Nalbandyan, V. B. Subsolidus phase relations, crystal chemistry and cation-transport properties of sodium iron antimony oxides. Solid State Sci. 2009, 11, 144– 150,  DOI: 10.1016/j.solidstatesciences.2008.04.014
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    69
    Subsolidus phase relations, crystal chemistry and cation-transport properties of sodium iron antimony oxides
    Politaev, V. V.; Nalbandyan, V. B.
    Solid State Sciences (2009), 11 (1), 144-150CODEN: SSSCFJ; ISSN:1293-2558. (Elsevier Masson SAS)
    Subsolidus phase relations in Na2O-Fe2O3-Sb2Ox system (excluding Na-rich and Sb-rich corners) were studied using powder X-ray diffraction. Samples were prepd. by conventional solid-state reactions at 980-1030 °C followed by quenching. Sb substitution for Fe stabilizes the low-temp. rhombohedral α form of NaFeO2 and enhances ionic cond.: σ(300 °C) = 0.5 S/m, E a = 0.38(3) eV, t e < 0.01 for Na0.8Fe0.9Sb0.1O2 ceramics. Besides known orthorhombic Na2Fe3SbO8, three new compds. have been identified: trigonal Na4FeSbO6, a superlattice of α-NaFeO2 type, a = 5.4217(7) Å, c = 16.2715(1) Å, possible space group P3112; orthorhombic Na2FeSbO5, possibly related to brownmillerite, Pbcn, a = 10.8965(13) Å, b = 15.7178(13) Å, c = 5.3253(4) Å, and one more phase with empirical formula Na4Fe3SbO9, whose pattern could not be indexed. Ion-exchange reactions lead to a delafossite-type superlattice Ag3(NaFeSb)O6 (a = 5.4503(12) Å, c = 18.7747(20) Å, possible space group P3112).
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  70. 70
    Arillo, M. A.; Lopez, M. L.; Perez-Cappe, E.; Pico, C.; Viega, M. L. Crystal structure and electrical properties of LiFeTiO4 spinel. Solid State Ionics 1998, 107, 307– 312,  DOI: 10.1016/S0167-2738(97)00537-7
    Google Scholar
    70
    Crystal structure and electrical properties of LiFeTiO4 spinel
    Arillo, M. A.; Lopez, M. L.; Perez-Cappe, E.; Pico, C.; Veiga, M. L.
    Solid State Ionics (1998), 107 (3,4), 307-312CODEN: SSIOD3; ISSN:0167-2738. (Elsevier Science B.V.)
    The complex oxide LiFeTiO4 was prepd. by an usual solid state method and its crystal structure was refined by Rietveld's anal. of powder x-ray diffraction data. These results indicate a spinel-type structure in which all Ti cations are in octahedral sites whereas Li and Fe cations are distributed on tetrahedral and octahedral sites, nearly in the same ratio, that could be expressed by the formula: (Li0.47Fe0.53)[Li0.53 Fe0.47Ti]O4. The ionic cond. measured on polycryst. samples was obtained by a.c. techniques at 473-873 K.
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  71. 71
    Kang, K.; Meng, Y. S.; Bréger, J.; Grey, C. P.; Ceder, G. Electrodes with high power and high capacity for rechargeable lithium batteries. Science 2006, 311, 977– 980,  DOI: 10.1126/science.1122152
    Google Scholar
    71
    Electrodes with High Power and High Capacity for Rechargeable Lithium Batteries
    Kang, Kisuk; Meng, Ying Shirley; Breger, Julien; Grey, Clare P.; Ceder, Gerbrand
    Science (Washington, DC, United States) (2006), 311 (5763), 977-980CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    New applications such as hybrid elec. vehicles and power backup require rechargeable batteries that combine high energy d. with high charge and discharge rate capability. Using ab initio computational modeling, strategies to design high-rate battery electrodes were identified. Tests were performed with [Li(Ni0.5Mn0.5)O2], a safe, inexpensive material that probably has poor intrinsic rate capability. Modification of its crystal structure provided unexpected high-rate capability, better than that of LiCoO2, the battery electrode material of choice.
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  72. 72
    Sai Gautam, G.; Canepa, P.; Urban, A.; Bo, S.-H.; Ceder, G. Influence of inversion on Mg mobility and electrochemistry in spinels. Chem. Mater. 2017, 29, 7918– 7930,  DOI: 10.1021/acs.chemmater.7b02820
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    72
    Influence of Inversion on Mg Mobility and Electrochemistry in Spinels
    Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Urban, Alexander; Bo, Shou-Hang; Ceder, Gerbrand
    Chemistry of Materials (2017), 29 (18), 7918-7930CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Magnesium oxide and sulfide spinels have recently attracted interest as cathode and electrolyte materials for energy-dense Mg batteries, but their obsd. electrochem. performance depends strongly on synthesis conditions. Using first-principles calcns. and percolation theory, we explore the extent to which spinel inversion influences Mg2+ ionic mobility in MgMn2O4 as a prototypical cathode, and MgIn2S4 as a potential solid electrolyte. We find that spinel inversion and the resulting changes of the local cation ordering give rise to both increased and decreased Mg2+ migration barriers, along specific migration pathways, in the oxide as well as the sulfide. To quantify the impact of spinel inversion on macroscopic Mg2+ transport, we det. the percolation thresholds in both MgMn2O4 and MgIn2S4. Furthermore, we analyze the impact of inversion on the electrochem. properties of the MgMn2O4 cathode via changes in the phase behavior, av. Mg insertion voltages and extractable capacities, at varying degrees of inversion. Our results confirm that inversion is a major performance limiting factor of Mg spinels and that synthesis techniques or compns. that stabilize the well-ordered spinel structure are crucial for the success of Mg spinels in multivalent batteries.
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  73. 73
    Bayliss, R. D.; Key, B.; Sai Gautam, G.; Canepa, P.; Kwon, B. J.; Lapidus, S. H.; Dogan, F.; Adil, A. A.; Lipton, A. S.; Baker, P. J.; Ceder, G.; Vaughey, J. T.; Cabana, J. Probing Mg migration in spinel oxides. Chem. Mater. 2020, 32, 663– 670,  DOI: 10.1021/acs.chemmater.9b02450
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    73
    Probing Mg Migration in Spinel Oxides
    Bayliss, Ryan D.; Key, Baris; Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Kwon, Bob Jin; Lapidus, Saul H.; Dogan, Fulya; Adil, Abdullah A.; Lipton, Andrew S.; Baker, Peter J.; Ceder, Gerbrand; Vaughey, John T.; Cabana, Jordi
    Chemistry of Materials (2020), 32 (2), 663-670CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Mg batteries utilizing oxide cathodes can theor. surpass the energy d. of current Li-ion technologies. The absence of functional devices so far has been ascribed to impeded Mg2+ migration within oxides, which severely handicaps intercalation reactions at the cathode. Broadly, knowledge of divalent cation migration in solid frameworks is surprisingly deficient. Here, we present a combined exptl. and theor. study of Mg migration within three spinel oxides, which reveal crit. features that influence it. Exptl. activation energies for a Mg2+ hop to an adjacent vacancy, as low as ∼0.6 eV, are reported. These barriers are low enough to support functional electrodes based on the intercalation of Mg2+. Subsequent electrochem. expts. demonstrate that significant demagnesiation is indeed possible, but the challenges instead lie with the chem. stability of the oxidized states. Our findings enhance the understanding of cation transport in solid structures and renew the prospects of finding materials capable of high d. of energy storage.
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  74. 74
    Kwon, B. J.; Yin, L.; Park, H.; Parajuli, R.; Kumar, K.; Kim, S.; Yang, M.; Murphy, M.; Zapol, P.; Liao, C.; Fister, T. T.; Klie, R. F.; Cabana, J.; Vaughey, J. T.; Lapidus, S. H.; Key, B. High voltage Mg-ion battery cathode via a solid solution Cr-Mn spinel oxide. Chem. Mater. 2020, 32, 6577– 6587,  DOI: 10.1021/acs.chemmater.0c01988
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    74
    High Voltage Mg-Ion Battery Cathode via a Solid Solution Cr-Mn Spinel Oxide
    Kwon, Bob Jin; Yin, Liang; Park, Haesun; Parajuli, Prakash; Kumar, Khagesh; Kim, Sanghyeon; Yang, Mengxi; Murphy, Megan; Zapol, Peter; Liao, Chen; Fister, Timothy T.; Klie, Robert F.; Cabana, Jordi; Vaughey, John T.; Lapidus, Saul H.; Key, Baris
    Chemistry of Materials (2020), 32 (15), 6577-6587CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Lattice Mg2+ in a tailored solid soln. spinel, MgCrMnO4, is electrochem. utilized at high Mn-redox potentials in a nonaq. electrolyte. Complementary evidence from exptl. and theor. analyses supports bulk Mg2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg2+ and O2- exists. Mg/Mn antisite inversion in the spinel is lowered to ~ 10% via postannealing at 350 °C to further improve Mg2+ mobility. Spinel lattice is preserved upon removal of Mg2+ without any phase transformations, denoting structural stability at the charged state at a high potential ~ 3.0 V (vs Mg/Mg2+). Clear remagnesiation upon first discharge, harvesting up to ~ 180 Wh/kg at 60 °C is shown. In the remagnesiated state, insertion of Mg2+ into interstitial sites in the spinel is detected, possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.
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  75. 75
    Robertson, A. D.; Tukamoto, H.; Irvine, J. T. S. Li1+xFe1–3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) based spinels: possible negative electrode materials for future Li-ion batteries. J. Electrochem. Soc. 1999, 146, 3958– 3962,  DOI: 10.1149/1.1392576
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    75
    Li1+xFe1-3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) based spinels: possible negative electrode materials for future Li-ion batteries
    Robertson, A. D.; Tukamoto, H.; Irvine, J. T. S.
    Journal of the Electrochemical Society (1999), 146 (11), 3958-3962CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    Members of the spinel solid soln. between LiFeTiO4 and Li4Ti5O12, i.e., Li1+xFe1-3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) have been investigated as possible neg. electrodes for future lithium-ion batteries. Electrochem. behavior and assocd. structural changes have been investigated over the potential range 0.01-2.6 V vs. Li+/Li. Results are promising with anodic capacities in excess of 200 mAh/g or ∼700 mAh/cm3 being obtained over 25 cycles for x = 0.33. Samples contg. Fe have reduced reversible capacity, however, the capacity below 1.00 VLi is greatly increased. A spinel-type structure is retained upon lithiation for all compns. studied, however, the degree of cation disorder increases with Fe content.
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  76. 76
    Miura, A.; Bartel, C. J.; Goto, Y.; Mizuguchi, Y.; Moriyoshi, C.; Kuroiwa, Y.; Wang, Y.; Yaguchi, T.; Shirai, M.; Nagao, M.; Rosero-Navarro, N. C.; Tadanaga, K.; Ceder, G.; Sun, W. Observing and modeling the sequential pairwise reactions that drive solid-state ceramic synthesis. Adv. Mater. 2021, 33, 2100312,  DOI: 10.1002/adma.202100312
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    76
    Observing and Modeling the Sequential Pairwise Reactions that Drive Solid-State Ceramic Synthesis
    Miura, Akira; Bartel, Christopher J.; Goto, Yosuke; Mizuguchi, Yoshikazu; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Wang, Yongming; Yaguchi, Toshie; Shirai, Manabu; Nagao, Masanori; Rosero-Navarro, Nataly Carolina; Tadanaga, Kiyoharu; Ceder, Gerbrand; Sun, Wenhao
    Advanced Materials (Weinheim, Germany) (2021), 33 (24), 2100312CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Solid-state synthesis from powder precursors is the primary processing route to advanced multicomponent ceramic materials. Designing reaction conditions and precursors for ceramic synthesis can be a laborious, trial-and-error process, as heterogeneous mixts. of precursors often evolve through a complicated series of reaction intermediates. Here, ab initio thermodn. is used to model which pair of precursors has the most reactive interface, enabling the understanding and anticipation of which non-equil. intermediates form in the early stages of a solid-state reaction. In situ X-ray diffraction and in situ electron microscopy are then used to observe how these initial intermediates influence phase evolution in the synthesis of the classic high-temp. superconductor YBa2Cu3O6+x (YBCO). The model developed herein rationalizes how the replacement of the traditional BaCO3 precursor with BaO2 redirects phase evolution through a low-temp. eutectic melt, facilitating the formation of YBCO in 30 min instead of 12+ h. Precursor selection plays an important role in tuning the thermodn. of interfacial reactions and emerges as an important design parameter in planning kinetically favorable synthesis pathways to complex ceramic materials.
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  77. 77
    Sun, W.; Dacek, S. T.; Ong, S. P.; Hautier, G.; Jain, A.; Richards, W. D.; Gamst, A. C.; Persson, K. A.; Ceder, G. The thermodynamic scale of inorganic crystalline metastability. Sci. Adv. 2016, 2, e1600225,  DOI: 10.1126/sciadv.1600225
    Google Scholar
    77
    The thermodynamic scale of inorganiccrystalline metastability
    Sun, Wenhao; Dacek, Stephen T.; Ong, Shyue Ping; Hautier, Geoffroy; Jain, Anubhav; Richards, William D.; Gamst, Anthony C.; Persson, Kristin A.; Ceder, Gerbrand
    Science Advances (2016), 2 (11), e1600225/1-e1600225/8CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)
    The space of metastable materials offers promising new design opportunities for next-generation technologicalmaterials such as complex oxides, semiconductors, pharmaceuticals, steels, and beyond. Although metastable phases are ubiquitous in both nature and technol., only a heuristic understanding of their underlying thermodn. exists. We report a large-scale data-mining study of the Materials Project, a high-through put database of d. functional theory calcd. energetics of Inorg. Crystal Structure Database structures,to explicitly quantify the thermodn. scale of metastability for 29,902 obsd. inorg. cryst. phases.We reveal the influence of chem. and compn. on the accessible thermodn. range of cryst. metastability for polymorphic and phase-sepg. compds., yielding new phys. insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compds. can necessarily besynthesized, and propose a principle of 'remnant metastability'-that observable metastable cryst. phases aregenerally remnants of thermodn. conditions where they were once the lowest free-energy phase.
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  78. 78
    Colbow, K.M.; Dahn, J.R.; Haering, R.R. Structure and electrochemistry of the spinel oxides LiTi2O4 and Li4/3Ti5/3O4. J. Power Sources 1989, 26, 397– 402,  DOI: 10.1016/0378-7753(89)80152-1
    Google Scholar
    78
    Structure and electrochemistry of the spinel oxides LiTi2O4 and Li4/3Ti5/3O4
    Colbow, K. M.; Dahn, J. R.; Haering, R. R.
    Journal of Power Sources (1989), 26 (3-4), 397-402CODEN: JPSODZ; ISSN:0378-7753.
    Li/LiTi2O4 and Li/Li4/3Ti5/3O4 batteries cycle reversibly with little capacity loss for >100 cycles, but have subtle differences in their voltage profiles. As the Li/LiTi2O4 cells have open-circuit voltage ∼2.0 V, the high voltage capacity at ∼2.8 V corresponds to removing Li from the spinel host. By contrast, Li/Li4/3Ti5/3O4 batteries do not show any capacity at high voltage that would correspond to a similar removal of Li from the Li4/3Ti5/3O4 host material. The differences in the battery behavior are interpreted based on the band structure of Li1+xTi2-xO4.
    >> More from SciFinder ®
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  79. 79
    Ohzuku, T.; Tatsumi, K.; Matoba, N.; Sawai, K. Electrochemistry and structural chemistry of Li[CrTi]O4 (Fd3̅m) in nonaqueous lithium cells. J. Electrochem. Soc. 2000, 147, 3592– 3597,  DOI: 10.1149/1.1393944
    Google Scholar
    79
    Electrochemistry and structural chemistry of Li[CrTi]O4 (Fd3m) in nonaqueous lithium cells
    Ohzuku, Tsutomu; Tatsumi, Koji; Matoba, Naoki; Sawai, Keijiro
    Journal of the Electrochemical Society (2000), 147 (10), 3592-3597CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    Li[CrTi]O4 (Fd3m; a = 8.32 Å) having a spinel-framework structure was prepd. and examd. in nonaq. lithium cells. Li/Li[CrTi]O4 cells showed the flat operating voltages of 1.50 V and rechargeable capacity of 150 mAh/g. The X-ray diffraction examns. in this region indicated that Li[CrTi]O4 was reduced to Li2[CrTi]O4 in a topotactic manner. Electrochem. oxidn. of Li[CrTi]O4 was also examd. Redox potential of 4.7 V vs. Li was obsd. while reversibility was poor due to the destruction of crystallite. Differences and similarities between Li[CrTi]O4 and Li[Li0.33Ti1.67]O4 were discussed with respect to operating voltage, reversibility, and insertion scheme.
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  80. 80
    Capponi, J. J.; Billat, S.; Bordet, P.; Lambert-Andron, B.; Souletie, B. Structure, superconducting properties and stoichiometry of Li1-xTi2O4 spinel single crystals. Phys. C 1991, 185–189, 2721– 2722,  DOI: 10.1016/0921-4534(91)91481-I
    Google Scholar
    80
    Structure, superconducting properties and stoichiometry of lithium titanate (Li1-xTi2O4) spinel single crystals
    Capponi, J. J.; Billat, S.; Bordet, P.; Lambert-Andron, B.; Souletie, B.
    Physica C: Superconductivity and Its Applications (Amsterdam, Netherlands) (1991), 185-189 (Pt. 4), 2721-2CODEN: PHYCE6; ISSN:0921-4534.
    It was shown that lithium can be extd. from the spinel LiTi2O4, with a large variation of the cubic cell parameter from a 8.41 to a 8.30 Å. The spinel network remains unchanged, but important differences in the x-ray diffraction intensities indicate a probable displacement of some titanium atoms. A dramatic change was obsd. in Tc which reach nearly 14 K for relatively small lithium extns.
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  81. 81
    de Picciotto, L. A.; Thackeray, M. M. Insertion/extraction reactions of lithium with LiV2O4. Mater. Res. Bull. 1985, 20, 1409– 1420,  DOI: 10.1016/0025-5408(85)90158-8
    Google Scholar
    81
    Insertion/extraction reactions of lithium with lithium vanadium oxide (LiV2O4)
    De Picciotto, L. A.; Thackeray, M. M.
    Materials Research Bulletin (1985), 20 (12), 1409-20CODEN: MRBUAC; ISSN:0025-5408.
    Li was inserted into and extd. from the spinel Li∼1.0V2O4 both electrochem. and chem. Electrochem. and structural data show that in Li1+xV2O4 (0 < x ≤ 0.5) Li+ ions are inserted into the interstitial octahedral sites of the Atet[B2]octX4 spinel structure. At x ≈ 0.5, Li+ ions in the tetrahedral A-sites are displaced into the remaining octahedral sites to yield, at x = 1, a rocksalt phase Li2V2O4; the [B2]X4 framework is unperturbed by the lithiation process. This framework also remains intact when Li+ ions are removed from Li∼1.0V2O4 to a compn. Li0.67V2O4. Further extn. of Li from the structure is accompanied by migration of some V ions from the B-sites to the interstitial octahedral sites of the spinel structure. This process reduces the crystal symmetry from cubic to trigonal symmetry. In Li0.27V2O4 the structure resembles that of Li0.22VO2, obtained by delithiation of layered LiVO2, in which the V cations are distributed in a 2:1 ratio between alternate cubic-close-packed O layers; in the LiV2O4 spinel this ratio is 3:1.
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  82. 82
    Barker, J.; Saidi, M. Y.; Swoyer, J. L. Electrochemical insertion properties of lithium vanadium titanate, LiVTiO4. Solid State Ionics 2004, 167, 413– 418,  DOI: 10.1016/j.ssi.2003.09.009
    Google Scholar
    82
    Electrochemical insertion properties of lithium vanadium titanate, LiVTiO4
    Barker, J.; Saidi, M. Y.; Swoyer, J. L.
    Solid State Ionics (2004), 167 (3-4), 413-418CODEN: SSIOD3; ISSN:0167-2738. (Elsevier Science B.V.)
    The electrochem. insertion properties of the novel spinel phase, lithium vanadium titanate, LiVTiO4 (Fd‾3m, a = 8.236 Å) have been evaluated in nonaq. lithium cells. LiVTiO4 is a member of the general series, LiMTiO4 where M represents a 3d transition metal and was synthesized by a simple solid-state ceramic approach involving lithium carbonate, V2O3 and TiO2. The lithium insertion behavior in the LiVTiO4 relies on the reversibility of the V3+/V4+ redox couple and preliminary electrochem. evaluation indicates a reversible sp. capacity of ∼90 mA-h/g, which represents the cycling of just over half the available lithium in the structure. High-resoln. measurements reveal a structureless and sloping voltage profile consistent with the lithium insertion reactions proceeding via a single-phase mechanism. The lithium extn. and insertion reactions are located at 3.16 and 2.85 V vs. Li, resp., while the sym. nature of the differential capacity data confirms the electrochem. reversibility. By comparison, the structurally related LiCrTiO4 phase demonstrates redox activity in the potential range 4.5-4.8 V vs. Li, although this behavior is accompanied by significant irreversibility. Const. current cycling of representative Li/LiVTiO4 cells indicates moderate insertion stability characterized by ∼15% capacity fade over the initial 20 cycles.
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  • Abstract

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    Figure 1

    Figure 1. CaFe2O4 structure. Gray spheres represent Na+. Green and blue octahedra represent the two symmetrically independent framework sites comprising the two “double rutile” chains.

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    Figure 2

    Figure 2. Schematic summarizing the synthetic approach and results presented in this paper. The ion combinations in green were successfully synthesized in the postspinel structure, whereas the ion combinations in red formed alternative phases.

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    Figure 3

    Figure 3. Rietveld refinement using synchrotron data for NaMg0.5Ti1.5O4. Blue crosses are the observed intensities, the green curve is the fitted pattern, the black curve is the difference pattern, and the red tick marks indicate the location of the CF-NaMg0.5Ti1.5O4 peaks.

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    Figure 4

    Figure 4. Powder XRD patterns for the 1:1:1 and 0.99:0.99:1.01 Na/Cr/Ti samples compared to a calculated pattern for the CF phase. Asterisks highlight peaks from the secondary phase Na0.6Cr0.6Ti0.4O2 in the 1:1:1 Na/Cr/Ti sample.

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    Figure 5

    Figure 5. A combinatorial representation of the Na-CF phase space. The phase-space shown covers all Na-CF compounds and combinations known to have been attempted in previous studies or this work. Conceivable but unexplored combinations (e.g., Sc3+ and Mo4+) are not depicted.

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    Figure 6

    Figure 6. 23Na solid-state NMR spectra at 12.5 kHz MAS and 9.4 T: (a) Na1.16In1.18Sb0.66O4, (b) Na0.96In0.96Sn1.04O4, and (c) “NaSc1.5Sb0.5O4” central transition resonances.

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    Figure 7

    Figure 7. Unit cell volume of the new Na-CFs versus the weighted-average effective ionic radius of the framework cations in octahedral coordination. (58)

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    Figure 8

    Figure 8. (a) Computed stability of NaxA3+B4+O4 and NaxA2+0.5B4+1.5O4 CF phases with three degrees of sodiation (x = 0, 0.5, 1.0). (b) Energy above hull of each xNa = 1 compound after including ideal mixing entropy for the octahedral cations at 1200 K. Green and red boxes show successful/failed syntheses at ambient pressure. (c) Energy difference between the CF and spinel structure. Note that the empty boxes correspond to In-containing compounds that failed to converge in either the CF or spinel structures and were consequently excluded from this analysis.

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  • References

    This article references 82 other publications.

    1. 1
      Bertraut, E.-F.; Blum, P.; Magnano, G. Structure des vanadite, chromite et ferrite monocalciques. Bull. Mineral. 1956, 79, 536– 561
      There is no corresponding record for this reference.
    2. 2
      Hill, P. M.; Peiser, H. S.; Rait, J. R. The crystal structure of calcium ferrite and β calcium chromite. Acta Crystallogr. 1956, 9, 981– 986,  DOI: 10.1107/S0365110X56002862
      2
      The crystal structure of calcium ferrite and β-calcium chromite
      Hill, Patricia M.; Peiser, H. S.; Rait, J. R.
      Acta Crystallographica (1956), 9 (), 981-6CODEN: ACCRA9; ISSN:0365-110X.
      Burdese's (Malgnori and Cirilli, Proc. Intern. Symposium on Chem. Cements. 3rd Symposium, London, 1952) cell dimensions (a = 9.16 ± 0.03, b = 10.67 ± 0.03, c = 3.012 ± 0.006 A.) are confirmed for Ca ferrite, which is isomorphous with β-Ca chromite and probably with Sr ferrite, but his statement about the close-packed hexagonal arrangement of O atoms is disproved. The space group is Pnam. The solution of the still incompletely refined structure from Patterson synthesis, Fourier projection, and 3-dimensional Fourier section at z = 1/4 is described. The residual disagreement factor, R, is 22%, this high value being due partly to pseudosymmetry. The crystal chemistry of the compd. is briefly discussed in relation to some of its phys. properties. The coordinations of Ca and Fe ions are normal.
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    3. 3
      Irifune, T.; Fujino, K.; Ohtani, E. A new high-pressure form of MgAl2O4. Nature 1991, 349, 409– 411,  DOI: 10.1038/349409a0
      3
      A new high-pressure form of magnesium aluminum spinel (MgAl2O4)
      Irifune, T.; Fujino, K.; Ohtani, E.
      Nature (London, United Kingdom) (1991), 349 (6308), 409-11CODEN: NATUAS; ISSN:0028-0836.
      The transformation of MgAl2O4 (I) spinel to a new high-pressure form at > 25 GPa in a multianvil high-pressure app. was studied. The new phase has a structure similar to that of CaFe2O4 (Ca ferrite) and its zero-pressure d. is 3.937(3) g/cm3, which is ∼2% denser than the lower-pressure assemblage of periclase + corundum. This high-pressure form of I may be an important host of Al in the Earth's lower mantle.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXhtVKhtro%253D&md5=bb39ceaf53fdb2322c3ab76d100fb651
    4. 4
      Funamori, N.; Jeanloz, R.; Nguyen, J. H.; Kavner, A.; Caldwell, W. A.; Fujino, K.; Miyajima, N.; Shinmei, T.; Tomioka, N. High-pressure transformations in MgAl2O4. J. Geophys. Res. Solid Earth 1998, 103, 20813– 20818,  DOI: 10.1029/98JB01575
      4
      High-pressure transformations in MgAl2O4
      Funamori, Nobumasa; Jeanloz, Raymond; Nguyen, Jeffrey H.; Kavner, Abby; Caldwell, Wendel A.; Fujino, Kiyoshi; Miyajima, Nobuyoshi; Shinmei, Toru; Tomioka, Naotaka
      Journal of Geophysical Research, [Solid Earth] (1998), 103 (B9), 20813-20818CODEN: JGEREE; ISSN:1934-8843. (American Geophysical Union)
      X ray diffraction and transmission electron microscopy on laser-heated diamond cell samples show that with increasing pressure MgAl2O4 spinel transforms first to Al2O3 corundum + MgO periclase, then to the CaFe2O4-structured phase, and finally to a new phase having the CaTi2O4 structure above ∼40 GPa. The CaFe2O4 and the CaTi2O4 structures are closely related and have almost the same densities and bulk moduli. Transformation from the CaFe2O4 to the CaTi2O4 phase would be expected to take place in oceanic crust that is subducted deep into the lower mantle.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmtFKlsLY%253D&md5=0fa84f0818ba0293dc51961ef76e5b15
    5. 5
      Liu, L. High pressure NaAlSiO4: the first silicate calcium ferrite isotype. Geophys. Res. Lett. 1977, 4, 183– 186,  DOI: 10.1029/GL004i005p00183
      5
      High pressure sodium aluminum silicate: the first silicate calcium ferrite isotype
      Liu, Lin-Gun
      Geophysical Research Letters (1977), 4 (5), 183-6CODEN: GPRLAJ; ISSN:0094-8276.
      At 100-180 kbars and ∼1000°, nepheline disproportionates into a mixt. of jadeite and α-NaAlO2. At >180 kbars, new x-ray diffraction lines began to appear and at 280 kbars, the sample was completely converted to the new phase. At >180 kbars, the mixt. of jadeite and α-NaAlO2 is inferred to react to form the Ca ferrite-type NaAlSiO4. It is the most closely packed A2SiO4 compd. known to date and appears to be the most likely host for Na in the earth's deep mantle.
      >> More from SciFinder ®
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    6. 6
      Yamada, H.; Matsui, Y.; Ito, E. Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure. Mineral. Mag. 1983, 47, 177– 181,  DOI: 10.1180/minmag.1983.047.343.07
      6
      Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure
      Yamada, Hirohisa; Matsui, Yoshito; Ito, Eiji
      Mineralogical Magazine (1983), 47 (343), 177-81CODEN: MNLMBB; ISSN:0026-461X.
      A high-pressure modification of NaAlSiO4 with Ca-ferrite structure was synthesized at > 24 GPa. The unit-cell dimensions are a ∼ 10.1546, h ∼ 8.6642, c ∼ 2.7385 Å, and V ∼ 24.93 Å3, with space group Pbnm. The calcd. d. is ∼ 3.916 g/cm3. Both M1O6 and M2O6 octahedra run parallel to the c axis, forming edge-shared double chains. The shared edges exhibit remarkable shortening (2.25-2.39 Å). Na atoms are located in the tunnel-type structure formed by the linked double chains being in 8-fold coordinations. The possible instability of the Ca-ferrite Mg2SiO4 is discussed.
      >> More from SciFinder ®
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    7. 7
      Reid, A. F.; Wadsley, A. D.; Ringwood, A. E. High pressure NaAlGeO4, a calcium ferrite isotype and model structure of silicates at depth in the earth’s mantle. Acta Crystallogr. 1967, 23, 736– 739,  DOI: 10.1107/S0365110X67003627
      7
      High pressure sodium aluminum germanate a calcium ferrite isotype and model structure for silicates at depth in the earth's mantle
      Reid, Allen Forrest; Wadsley, Arthur D.; Ringwood, Alfred E.
      Acta Crystallographica (1967), 23 (5), 736-9CODEN: ACCRA9; ISSN:0365-110X.
      The high pressure phase NaAlGeO4 formed at 120 kilobars and 900° has the Ca ferrite structure, space group Pnma, unit-cell dimensions a 8.87, b 2.84, c 10.40 A.; dx is 4.73. The isomorphous silicate NaAlSiO4 (dx = 3.9 ± 0.1), should exist in the earth's mantle, being transformed by pressure from nepheline or jadeite.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXnt1Gm&md5=bc418c5a7604be4ec1af4f76aa040fab
    8. 8
      Reid, A. F.; Wadsley, A. D.; Sienko, M. J. Crystal chemistry of sodium scandium titanate, NaScTiO4, and its isomorphs. Inorg. Chem. 1968, 7, 112– 118,  DOI: 10.1021/ic50059a024
      8
      Crystal chemistry of sodium scandium titanate, NaScTiO4, and its isomorphs
      Reid, Allen Forrest; Wadsley, Arthur D.; Sienko, Michell J.
      Inorganic Chemistry (1968), 7 (1), 112-18CODEN: INOCAJ; ISSN:0020-1669.
      NaScTiO4, NaFeTiO4, NaScSnO4, NaFeSnO4, NaScZrO4, and NaScHfO4, as well as high-pressure NaAlGeO, are strictly isomorphous with the orthorhombic Ca ferrite type structure, space group Pnma. Each pair of tri-and quadrivalent elements randomly occupies two sets of crystallographically nonequiv. octahedral positions in the structure, the local site symmetries of which are almost identical. Uniform bond lengths and normal thermal vibration parameters for the randomized atoms in NaScTiO4, detd. by single-crystal structure analysis, are interpreted to mean that the randomness of the ions Sc3+ and Ti4+ leads to a real averaging of ionic sizes. No Ca ferrite structure was found by replacing Na with Li, K, Rb, or Cs nor for the NaA3+B4+O4 compds. where A3+ = Mn, Cr, Co, or In, although a no. of other phases were formed. Ca ferrite isotypes form only when A3+ and B4+ can be constrained to match one another both in size and in a local site symmetry which is nearly spherical. 45 references.
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    9. 9
      Ishii, T.; Sakai, T.; Kojitani, H.; Mori, D.; Inaguma, Y.; Matsushita, Y.; Yamaura, K.; Akaogi, M. High-pressure phase relations and crystal structures of postpinel phases in MgV2O4, FeV2O4, and MnCr2O4: crystal chemistry of AB2O4 postspinel compounds. Inorg. Chem. 2018, 57, 6648– 6657,  DOI: 10.1021/acs.inorgchem.8b00810
      9
      High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds
      Ishii, Takayuki; Sakai, Tsubasa; Kojitani, Hiroshi; Mori, Daisuke; Inaguma, Yoshiyuki; Matsushita, Yoshitaka; Yamaura, Kazunari; Akaogi, Masaki
      Inorganic Chemistry (2018), 57 (11), 6648-6657CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      We have investigated high-pressure, high-temp. phase transitions of spinel (Sp)-type MgV2O4, FeV2O4, and MnCr2O4. At 1200-1800 °C, MgV2O4 Sp decomps. at 4-7 GPa into a phase assemblage of MgO periclase + corundum (Cor)-type V2O3, and they react at 10-15 GPa to form a phase with a calcium titanite (CT)-type structure. FeV2O4 Sp transforms to CT-type FeV2O4 at 12 GPa via decompn. phases of FeO wustite + Cor-type V2O3. MnCr2O4 Sp directly transforms to the calcium ferrite (CF)-structured phase at 10 GPa and 1000-1400 °C. Rietveld refinements of CT-type MgV2O4 and FeV2O4 and CF-type MnCr2O4 confirm that both the CT- and CF-type structures have frameworks formed by double chains of edge-shared B3+O6 octahedra (B3+ = V3+ and Cr3+) running parallel to one of orthorhombic cell axes. A relatively large A2+ cation (A2+ = Mg2+, Fe2+, and Mn2+) occupies a tunnel-shaped space formed by corner-sharing of four double chains. Effective coordination nos. calcd. from eight neighboring oxygen-A2+ cation distances of CT-type MgV2O4 and FeV2O4 and CF-type MnCr2O4 are 5.50, 5.16, and 7.52, resp. This implies that the CT- and CF-type structures practically have trigonal prism (six-coordinated) and bicapped trigonal prism (eight-coordinated) sites for the A2+ cations, resp. A relationship between cation sizes of VIIIA2+ and VIB3+ and crystal structures (CF- and CT-types) of A2+B23+O4 is discussed using the above new data and available previous data of the postspinel phases. We found that CF-type A2+B23+O4 crystallize in wide ionic radius ranges of 0.9-1.4 Å for VIIIA2+ and 0.55-1.1 Å for VIB3+, whereas CT-type phases crystallize in very narrow ionic radius ranges of ∼0.9 Å for VIIIA2+ and 0.6-0.65 Å for VIB3+. This would be attributed to the fact that the tunnel space of CT-type structure is geometrically less flexible due to the smaller coordination no. for A2+ cation than that of CF-type.
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    10. 10
      Yamaura, K.; Huang, Q.; Zhang, L.; Takada, K.; Baba, Y.; Nagai, T.; Matsui, Y.; Kosuda, K.; Takayama-Muromachi, E. Spinel-to-CaFe2O4-type structural transformation in LiMn2O4 under higher pressure. J. Am. Chem. Soc. 2006, 128, 9448– 9456,  DOI: 10.1021/ja0612302
      10
      Spinel-to-CaFe2O4-Type Structural Transformation in LiMn2O4 under High Pressure
      Yamaura, Kazunari; Huang, Qingzhen; Zhang, Lianqi; Takada, Kazunori; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Kosuda, Kosuke; Takayama-Muromachi, Eiji
      Journal of the American Chemical Society (2006), 128 (29), 9448-9456CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A new form of LiMn2O4 is reported. The structure is the CaFe2O4-type and 6% denser than the spinel. The structure transformation was achieved by heating at 6 GPa. Anal. of the neutron diffraction pattern confirmed an av. of the structure; the unit cell was orthorhombic at a 8.8336(5), b 2.83387(18), and c 10.6535(7) Å (Pnma). Electron diffraction patterns indicated an order of superstructure 3a × b × c, which might be initiated by Li vacancies. The exact compn. is estd. at Li0.92Mn2O4 from the structure anal. and quantity of intercalated Li. The polycryst. CaFe2O4-type compd. showed semiconducting-like characters over the studied range >5 K. The activation energy was reduced to ∼0.27 eV from ∼0.40 eV at the spinel form, suggesting a possible enhancement of hopping mobility. Magnetic and specific-heat data indicated a magnetically glassy transition at ∼10 K. As the CaFe2O4-type transition was obsd. for the mineral MgAl2O4, hence the new form of the Li Mn oxide would provide valuable opportunities to study not only the magnetism of strongly correlated electrons but also the thermodn. of the phase transition in the mantle.
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    11. 11
      Yamaura, K.; Arai, M.; Sato, A.; Karki, A. B.; Young, D. P.; Movshovich, R.; Okamoto, S.; Mandrus, D.; Takayama-Muromachi NaV2O4: a quasi-1D metallic antiferromagnet with half-metallic chains. Phys. Rev. Lett. 2007, 99, 196601,  DOI: 10.1103/PhysRevLett.99.196601
      11
      NaV2O4: A Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains
      Yamaura, K.; Arai, M.; Sato, A.; Karki, A. B.; Young, D. P.; Movshovich, R.; Okamoto, S.; Mandrus, D.; Takayama-Muromachi, E.
      Physical Review Letters (2007), 99 (19), 196601/1-196601/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      NaV2O4 crystals were grown under high pressure using a NaCl flux, and the crystals were characterized with x-ray diffraction, elec. resistivity, heat capacity, and magnetization. The structure of NaV2O4 consists of double chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic, with the resistivity perpendicular to the chains >20 times greater than that parallel to the chains. Magnetically, the intrachain interactions are ferromagnetic and the interchain interactions are antiferromagnetic; 3-dimensional antiferromagnetic order is established at 140 K. First-principles electronic structure calcns. indicate that the chains are half-metallic. The case of NaV2O4 seems to be a quasi-1D analog of what was found for half-metallic materials.
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    12. 12
      Sakurai, H.; Kolodiazhnyi, T.; Michiue, Y.; Takayama-Muromachi, E.; Tanabe, Y.; Kikuchi, H. Unconventional colossal magnetoresistance in sodium chromium oxide with a mixed-valence state. Angew. Chem. 2012, 124, 6757– 6760,  DOI: 10.1002/ange.201201884
      There is no corresponding record for this reference.
    13. 13
      Young, O.; Wildes, A. R.; Manuel, P.; Ouladdiaf, B.; Khalyavin, D. D.; Balakrishnan, G.; Petrenko, O. A. Highly frustrated magnetism in SrHo2O4: coexistence of two types of short-range order. Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 88, 024411,  DOI: 10.1103/PhysRevB.88.024411
      13
      Highly frustrated magnetism in SrHo2O4. Coexistence of two types of short-range order
      Young, O.; Wildes, A. R.; Manuel, P.; Ouladdiaf, B.; Khalyavin, D. D.; Balakrishnan, G.; Petrenko, O. A.
      Physical Review B: Condensed Matter and Materials Physics (2013), 88 (2), 024411/1-024411/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      SrHo2O4 is a geometrically frustrated magnet in which the magnetic Ho3+ ions form honeycomb layers connected through a network of zigzag chains. At low-temp. 2 distinct types of short-range magnetic order can be inferred from single-crystal diffraction data, collected using both polarized and unpolarized neutrons. In the (hk0) plane the diffuse scattering is most noticeable around the k = 0 positions and its intensity rapidly increases at temps. below 0.7 K. In addn., planes of diffuse scattering at Q = (hk ± 1/2) are visible at temps. as high as 4.5 K. These planes coexist with the broad peaks of diffuse scattering in the (hk0) plane at low temps. Correlation lengths assocd. with the broad peaks are L ≈ 150 Å in the a-b plane and L ≈ 190 Å along the c axis, while the correlation length assocd. with the diffuse scattering planes is L ≈ 230 Å along the c axis at the lowest temp. Both types of diffuse scattering are elastic in nature. The highly unusual coexistence of the two types of diffuse scattering in SrHo2O4 is likely to be the result of the presence of two crystallog. inequivalent sites for Ho3+ in the unit cell.
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    14. 14
      Dutton, S. E.; Broholm, C. L.; Cava, R. J. Divergent effects of static disorder and hole doping in geometrically frustrated β-CaCr2O4. J. Solid State Chem. 2010, 183, 1798– 1804,  DOI: 10.1016/j.jssc.2010.05.032
      14
      Divergent effects of static disorder and hole doping in geometrically frustrated β-CaCr2O4
      Dutton, S. E.; Broholm, C. L.; Cava, R. J.
      Journal of Solid State Chemistry (2010), 183 (8), 1798-1804CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
      The gallium substituted and calcium deficient variants of geometrically frustrated β-CaCr2O4, β-CaCr2-2xGa2xO4 (0.02≤x≤0.25) and β-Ca1-yCr2O4 (0.075≤y≤0.15), were studied by x-ray powder diffraction, magnetization and sp. heat measurements. This allows for a direct comparison of the effects, in a geometrically frustrated magnet, of the static disorder that arises from nonmagnetic substitution and the dynamic disorder that arises from hole doping. In both cases, disturbing the Cr3+ lattice results in a redn. in the degree of magnetic frustration. On substitution of Ga, which introduces disorder without creating holes, a gradual release of spins from ordered antiferromagnetic states is obsd. In contrast, in the calcium-deficient compds. the introduction of holes induces static ferrimagnetic ordering and much stronger perturbations of the β-CaCr2O4 host.
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    15. 15
      Arévalo-López, Á. M.; Dos santos-García, A. J.; Castillo-Martínez, E.; Durán, A.; Alario-Franco, M. Á. Spinel to CaFe2O4 transformation: Mechanism and properties of β-CdCr2O4. Inorg. Chem. 2010, 49, 2827– 2833,  DOI: 10.1021/ic902228h
      15
      Spinel to CaFe2O4 Transformation: Mechanism and Properties of β-CdCr2O4
      Arevalo-Lopez, Angel M.; Dos santos-Garcia, Antonio J.; Castillo-Martinez, Elizabeth; Duran, Alejandro; Alario-Franco, Miguel A.
      Inorganic Chemistry (2010), 49 (6), 2827-2833CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      The CdCr2O4 spinel transforms to a 10.6% denser new polymorph of the CaFe2O4-type structure at 10 GPa and 1100°. This new polymorph has a honeycomb-like structure because of double rutile-type chains formed by [Cr-O6] edge-shared octehedra. This crystal structure is prone to be magnetically frustrated and presents low-dimensional antiferromagnetism at 25 K < T < 150 K, accompanied by more complex interactions as the temp. decreases. These transitions are evidenced by magnetic susceptibility and heat capacity measurements. We also discuss a possible structural mechanism for the transformation.
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    16. 16
      Shimomura, Y.; Kurushima, T.; Kijima, N. Photoluminescence and crystal structure of green-emitting phosphor CaSc2O4:Ce3+. J. Electrochem. Soc. 2007, 154, J234,  DOI: 10.1149/1.2741172
      16
      Photoluminescence and Crystal Structure of Green-Emitting Phosphor CaSc2O4:Ce3+
      Shimomura, Yasuo; Kurushima, Tomoyuki; Kijima, Naoto
      Journal of the Electrochemical Society (2007), 154 (8), J234-J238CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      A new green phosphor, Ce3+-act5ivated CaSc2O4, was developed, which shows green luminescence with a peak wavelength of 515 nm under excitation with blue light. Ce3+-activated CaSc2O4 can be used as a material for color conversion of white-light-emitting diodes (LEDs), which consist of a blue LED, a green phosphor, and a red phosphor, because the luminescence efficiency of this phosphor is comparable to those of com. phosphors such as Y3Al5O12:Ce3+. The host crystal of this phosphor has an orthorhombic CaFe2O4 structure, and the Ce ion probably exists in an eight-coordinated Ca position. The authors studied the dependency of the firing temp. and dopant concn. for luminescence intensity and found that the optimum temp. and concn. were 1600° and 1 mol % of Ce substituted to the Ca position. The luminescence peak wavelength was shifted toward longer wavelengths by replacing Ca with Mg. In contrast, replacing Ca with Sr resulted in a shift toward shorter wavelengths.
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    17. 17
      Hao, Z.; Zhang, J.; Zhang, X.; Lu, S.; Wang, X. Blue-green-emitting phosphor CaSc2O4:Tb3+: tunable luminescence manipulated by cross-relaxation. J. Electrochem. Soc. 2009, 156, H193,  DOI: 10.1149/1.3060382
      17
      Blue-Green-Emitting Phosphor CaSc2O4:Tb3+: Tunable Luminescence Manipulated by Cross-Relaxation
      Hao, Zhendong; Zhang, Jiahua; Zhang, Xia; Lu, Shaozhe; Wang, Xiaojun
      Journal of the Electrochemical Society (2009), 156 (3), H193-H196CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      Blue-green CaSc2O4:Tb3+ phosphors were prepd. by solid-state reaction. Under 254 or 276 nm light excitation, both blue and green emissions are obsd., which are attributed to the characteristic 4f-4f transitions (5D3,4-7FJ, J = 6, 5, 4, 3) of Tb3+. The cross-relaxation from 5D3 to 5D4 states are studied by spectroscopic and dynamic measurements. The luminescent color of CaSc2O4:Tb3+ can be tuned from blue to green by manipulating the cross-relaxation. Also, efficient white light is generated for fluorescence lamps by blending the blue-green CaSc2O4:Tb3+ with a red CaSc2O4:Eu3+ phosphor.
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    18. 18
      Hao, Z.; Zhang, J.; Zhang, X.; Wang, X. CaSc2O4:Eu3+: A tunable full-color emitting phosphor for white light emitting diodes. Opt. Mater. 2011, 33, 355– 358,  DOI: 10.1016/j.optmat.2010.09.035
      18
      CaSc2O4:Eu3+: A tunable full-color emitting phosphor for white light emitting diodes
      Hao, Zhendong; Zhang, Jiahua; Zhang, Xia; Wang, Xiaojun
      Optical Materials (Amsterdam, Netherlands) (2011), 33 (3), 355-358CODEN: OMATET; ISSN:0925-3467. (Elsevier B.V.)
      We report an intense full-color emission originating from 5D0,1,2,3 to 7F0,1,2,3,4 transitions of Eu3+ in CaSc2O4 upon 395 nm excitation. The emission spectra vary with increasing Eu3+ concn., demonstrating tunable color coordinates from white to red region in the CIE chromaticity diagram. Considering the relaxation from 5DJ to 5DJ -1 through cross energy transfer, the Eu3+ concn. dependent emission spectra are well simulated based on the anal. of steady state rate equations and the measured lifetimes of the 5DJ levels. It is suggested that CaSc2O4:Eu3+ could be a potential single-phased full-color emitting phosphor for near-UV InGaN chip pumped white light emitting diodes.
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    19. 19
      Bruno, S. R.; Blakely, C. K.; Clapham, J. B.; Davis, J. D.; Bi, W.; Alp, E. E.; Poltavets, V. V. Synthesis and electrochemical properties of novel LiFeTiO4 and Li2FeTiO4 polymorphs with the CaFe2O4-type structures. J. Power Sources 2015, 273, 396– 403,  DOI: 10.1016/j.jpowsour.2014.09.115
      19
      Synthesis and electrochemical properties of novel LiFeTiO4 and Li2FeTiO4 polymorphs with the CaFe2O4-type structures
      Bruno, Shaun R.; Blakely, Colin K.; Clapham, Jonathon B.; Davis, Joshua D.; Bi, Wenli; Alp, E. Ercan; Poltavets, Viktor V.
      Journal of Power Sources (2015), 273 (), 396-403CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      The new LiFeTiO4 polymorph with the CaFe2O4-type (CF) crystal structure was synthesized via ion exchange from NaFeTiO4. Due to the presence of tunnels sufficiently large to accommodate addnl. Li+ ions, CF-LiFeTiO4 was studied as a model compd. for potential cathode material utilizing Fe2+/Fe3+ (on Li intercalation) as well as Fe3+/Fe4+ (on Li deintercalation) redox couples. Chem. and electrochem. Li intercalation preserves the structural motif of CF-LiFeTiO4 and results in Li2FeTiO4 compd. The electrochem. cycling of CF-LiFeTiO4 vs. Li occurs between 2 and 2.3 V with an initial specific capacity of 148 mA-h/g. High Li+ ionic cond. in the compd. is suggested based on the interconnection of Li+ bond valence sum isosurfaces at a bond valence sum value of 1.0. Chem. Li deintercalation from CF-LiFeTiO4 results in compd. decompn. without Fe4+ formation, as confirmed by Moessbauer spectroscopy.
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    20. 20
      Jung, Y. H.; Kim, D. K.; Hong, S.-T. Synthesis, structure, and electrochemical Li-ion intercalation of LiRu2O4 with CaFe2O4-type structure. J. Power Sources 2013, 233, 285– 289,  DOI: 10.1016/j.jpowsour.2013.01.119
      20
      Synthesis, structure, and electrochemical Li-ion intercalation of LiRu2O4 with CaFe2O4-type structure
      Jung, Young Hwa; Kim, Do Kyung; Hong, Seung-Tae
      Journal of Power Sources (2013), 233 (), 285-289CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      A new material, LiRu2O4, has been synthesized by ion-exchange reaction from NaRu2O4 that has been prepd. by solid state reaction at 950° under Ar flow. The crystal structure of LiRu2O4, isostructural with the parent NaRu2O4, has been refined by an x-ray Rietveld method (Pnma, a = 9.13940(5) Å, b = 2.80070(9) Å, c = 11.0017(1) Å, Z = 4, Rp = 5.30%, wRp = 6.73%, χ2 = 0.41, 23°). The structure belongs to CaFe2O4-type, where double chains of edge-sharing octahedral RuO6 share the corners with neighboring double chains and form tunnels in between them parallel to the shortest b-axis so that the one-dimensional Li array is placed inside each of the tunnels. Detailed structural anal. indicates that the tunnel inside has more than enough space to be filled with the Li atoms. The electrochem. tests of LiRu2O4 demonstrates a reversible Li intercalation reaction at 3.2-3.5 V vs. Li/Li+ with a capacity of ∼80 mA-h/g. The material exhibits excellent high-rate characteristics (93% capacity retention at 10C/1C) as well as high capacity retention with cycles (99% at 50 cycles).
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    21. 21
      Sun, X.; Blanc, L.; Nolis, G. M.; Bonnick, P.; Cabana, J.; Nazar, L. F. NaV1.25Ti0.75O4: a potential post-spinel cathode material. Chem. Mater. 2018, 30, 121– 128,  DOI: 10.1021/acs.chemmater.7b03383
      21
      NaV1.25Ti0.75O4: A Potential Post-Spinel Cathode Material for Mg Batteries
      Sun, Xiaoqi; Blanc, Lauren; Nolis, Gene M.; Bonnick, Patrick; Cabana, Jordi; Nazar, Linda F.
      Chemistry of Materials (2018), 30 (1), 121-128CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Rechargeable Mg batteries are promising candidates for high energy d. storage in theory, when a Mg metal anode is combined with an oxide cathode material. Despite the widely obsd. sluggish Mg2+ diffusion in most oxide lattices, recent first-principles calcns. predicted low diffusion barriers in the calcium ferrite (CF)-type post-spinel structures. In the present work, we exptl. examine the prospect of CF-type NaV1.25Ti0.75O4 as a Mg cathode. The Na+ ions, which lie in the ion migration pathway, need to be removed or exchanged with Mg2+ to allow Mg2+ de/intercalation. Partial desodiation was achieved through chem. and electrochem. methods, as proven by X-ray diffraction and X-ray absorption spectroscopy, but deep desodiation was accompanied by partial amorphization of the material. Mg2+ ion exchange at moderate temp. (80 °C) resulted in the formation of Na0.19Mg0.41V1.25Ti0.75O4; however, phase transformation was obsd. when higher temps. were applied to attempt complete ion exchange. Such phenomena point to the instability of the CF lattice when the tunnel is empty or occupied by a small ion (Mg2+). Thus, while the low migration barrier predicted by computation is partly based on the relative metastability of the theor. CF-MgxV1.25Ti0.75O4 lattice, the difficulty in stabilizing it also renders the material synthetically nonaccessible, hindering this post-spinel's application as an electrode material.
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    22. 22
      Mukai, K.; Uyama, T.; Yamada, I. Structural and electrochemical analyses on the transformation of CaFe2O4-type LiMn2O4 from spinel-type LiMn2O4. ACS Omega 2019, 4, 6459– 6467,  DOI: 10.1021/acsomega.9b00588
      22
      Structural and Electrochemical Analyses on the Transformation of CaFe2O4-Type LiMn2O4 from Spinel-Type LiMn2O4
      Mukai, Kazuhiko; Uyama, Takeshi; Yamada, Ikuya
      ACS Omega (2019), 4 (4), 6459-6467CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      Lithium manganese oxides have received much attention as pos. electrode ma- terials for lithium-ion batteries. In this study, a post-spinel material, CaFe2O4-type LiMn2O4 (CF-LMO), was synthesized at high pressures above 6 GPa, and its crystal structure and electrochem. properties were examd. CF-LMO exhibits a one- dimensional (1D) conduction pathway for Li ions, which is predicted to be superior to the three-dimensional conduction pathway for these ions. The stoichiometric LiMn2O4 spinel (SP-LMO) was decompd. into three phases of Li2MnO3, MnO2, and Mn2O3 at 600° C, and then started to transform into the CF-LMO structure above 800° C. The rechargeable capacity (Qrecha) of the sample synthesized at 1000° C was limited to 40 mAhg1 in the voltage range between 1.5 and 5.3 V, due to the presence of a small amt. of Li2MnO3 phase in the sample (= 9.1 wt%). In addn., the Li-rich spinels, Li[LixMn2x]O4 with x = 0.1, 0.2, and 0.333, were also employed for the synthesis of CF-LMO. The sample prepd. from x = 0.2 exhibited a Qrecha value exceeding 120 mAhg1 with stable cycling performance, despite the presence of large amts. of the phases Li2MnO3, MnO2, and Mn2O3. Details of the structural transformation from SP-LMO to CF-LMO and the effect of Mn ions on the 1D conduction pathway are discussed.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmslOrsbY%253D&md5=822187d6cccb461066e5bab996d6b924
    23. 23
      Nolis, G.; Gallardo-Amores, J. M.; Serrano-Sevillano, J.; Jahrman, E.; Yoo, H. D.; Hu, L.; Hancock, J. C.; Bolotnikov, J.; Kim, S.; Freeland, J. W.; Liu, Y.-S.; Poeppelmeier, K. R.; Seidler, G. T.; Guo, J.; Alario-Franco, M. A.; Casas-Cabanas, M.; Morán, E.; Cabana, J. Factors defining the intercalation electrochemistry of CaFe2O4-type manganese oxides. Chem. Mater. 2020, 32, 8203– 8215,  DOI: 10.1021/acs.chemmater.0c01858
      23
      Factors Defining the Intercalation Electrochemistry of CaFe2O4-Type Manganese Oxides
      Nolis, Gene; Gallardo-Amores, Jose M.; Serrano-Sevillano, Jon; Jahrman, Evan; Yoo, Hyun Deog; Hu, Linhua; Hancock, Justin C.; Bolotnikov, Jannie; Kim, Soojeong; Freeland, John W.; Liu, Yi-Sheng; Poeppelmeier, Kenneth R.; Seidler, Gerald T.; Guo, Jinghua; Alario-Franco, Miguel A.; Casas-Cabanas, Montse; Moran, Emilio; Cabana, Jordi
      Chemistry of Materials (2020), 32 (19), 8203-8215CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Oxides with the CaFe2O4-type structure were predicted as being suitable hosts for reactions of intercalation of light cations such as Li and Mg because of their favorable cationic diffusion. Although Li was shown to intercalate into the Mn2O4 variant, the key structure property correlations detg. function are not fully ascertained. This basic information is needed before attempting the intercalation of divalent cations, which face comparably higher migration barriers. For this purpose, the electrode function of CaFe2O4-type Li0.8Mn2O4 was compared for materials made by a direct high-pressure route or through cation exchange from NaMn2O4. X-ray diffraction and absorption spectroscopy revealed that, despite having largely the same bulk structure, the presence of surface defects blocked Li+ transfer in Li0.8Mn2O4 made at high pressure. These defects were not present in the cation-exchanged material, which resulted in highly reversible Li intercalation with very fast kinetics in micrometric crystals. Delithiated electrodes from the cation-exchange synthesis were subsequently reduced in an ionic liq. electrolyte contg. Mg2+. The process induced topotactic changes in the bulk, strongly suggesting the existence of intercalation, but it is accompanied by severe reactivity with the electrolyte that impedes reversibility. This study uncovers that defects affect the fundamentals of cation intercalation in this novel class of materials. The ability of the cation-exchanged material to conduct fast reactions with Li is consistent with calcd. activation energy barriers and creates promise for their use as Mg hosts, provided that novel electrolytes enhanced stability at high potential can be realized.
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    24. 24
      Liu, X.; Wang, X.; Iyo, A.; Yu, H.; Li, D.; Zhou, H. High stable post-spinel NaMn2O4 cathode of sodium ion battery. J. Mater. Chem. A 2014, 2, 14822– 14826,  DOI: 10.1039/C4TA03349C
      24
      High stable post-spinel NaMn2O4 cathode of sodium ion battery
      Liu, Xizheng; Wang, Xi; Iyo, Akira; Yu, Haijun; Li, De; Zhou, Haoshen
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (36), 14822-14826CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      A spinel-type NaMn2O4 based on an inventive Mn and Na compd. was synthesized under high pressure (4.5 GPa) for use as the cathode of a Na ion battery. It exhibits a 1-step voltage profile, limited polarization and good capacity retention both at room and high temps. The capacity retention is 94% after 200 cycles at room temp. The stable battery performance is due to the high barrier of structure rearrangement and suppressed Jahn-Teller distortions in this post spinel structure.
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    25. 25
      Chiring, A.; Senguttuvan, P. Chemical pressure-stabilized post spinel-NaMnSnO4 as potential cathode for sodium-ion batteries. Bull. Mater. Sci. 2020, 43, 306,  DOI: 10.1007/s12034-020-02203-6
      25
      Chemical pressure-stabilized post spinel-NaMnSnO4 as potential cathode for sodium-ion batteries
      Chiring, Aditi; Senguttuvan, Premkumar
      Bulletin of Materials Science (2020), 43 (1), 306CODEN: BUMSDW; ISSN:0250-4707. (Indian Academy of Sciences)
      Spinel LiMn2O4 is a popular cathode material in lithium-ion batteries due to its high operating voltage and reversible specific capacity. Synthesizing analogus NaMn2O4 in the spinel structure, for sodium-ion batteries, is challenging due to the thermodn. instability of the compd., mostly arising due to Jahn-Teller distortion of the Mn3+ center. However, post-spinel NaMn2O4 (named as such because the compds. were initially achieved by subjecting a spinel phase to high pressure) could be synthesized at a high temp. and pressure (1373 K and 4.5 GPa, resp.) and is found to be stable at std. conditions. Also, these compds. have a lower ion diffusion barrier than their resp. spinels. In this work, an attempt has been made to induce chem. pressure within the system by the use of a heavy cation, i.e., Sn4+ in the framework, to synthesize post-spinel NaMnSnO4 at ambient pressure conditions. The as-prepd. NaMnSnO4 samples are characterized with SEM, X-ray diffraction, inductively coupled plasma-at. emission spectroscopy and galvanostatic cycling with potential limitation measurements.
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    26. 26
      Ling, C.; Mizuno, F. Phase stability of post-spinel compound AMn2O4 (A = Li, Na, or Mg) and its application as a rechargeable battery cathode. Chem. Mater. 2013, 25, 3062– 3071,  DOI: 10.1021/cm401250c
      26
      Phase stability of post-spinel compound AMn2O4 (A = Li, Na, or Mg) and its application as a rechargeable battery cathode
      Ling, Chen; Mizuno, Fuminori
      Chemistry of Materials (2013), 25 (15), 3062-3071CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      At high pressures, spinel compds. can transform to CaFe2O4, CaMn2O4, or CaTi2O4 phases, which are regarded as post-spinel phases. Here, first-principles calcns. are used to systematically study the stability of post-spinel LiMn2O4, NaMn2O4, and MgMn2O4, as well as their potential application as rechargeable battery cathodes. Thermodynamically, the stability of the post-spinel phase is highly related to the electronic configuration of transition-metal ions. By changing the concn. of Jahn-Teller active Mn3+, the relative stabilities of post-spinel phases can be easily monitored. It provides a practical way to obtain post-spinel compds. with desirable structures. Kinetically, post-spinel phases can be stable under ambient conditions, because of the high barrier that must be overcome to rearrange MnO6 octahedrons. The most spectacular finding in this work is the high cationic mobility in post-spinel compds. The activation energy barrier of the migration of Mg2+ in CaFe2O4-type MgMn2O4 is 0.4 eV, suggesting that the mobility of Mg2+ in this compd. is comparable to that of Li+ in typical Li-ion battery cathodes. To explore the potential application of post-spinel compds. as rechargeable battery cathodes, the voltage profile for the electrochem. insertion/removal of Mg in CaFe2O4-type MgMn2O4 is predicted. Its theor. energy d. is 1.3 times greater than that of typical Li-ion battery cathodes. These outstanding properties make CaFe2O4-type MgMn2O4 an attractive cathode candidate for rechargeable Mg batteries.
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    27. 27
      Hannah, D. C.; Sai Gautam, G.; Canepa, P.; Rong, Z.; Ceder, G. Magnesium ion mobility in post-spinels accessible at ambient pressure. Chem. Commun. 2017, 53, 5171– 5174,  DOI: 10.1039/C7CC01092C
      27
      Magnesium ion mobility in post-spinels accessible at ambient pressure
      Hannah, Daniel C.; Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Rong, Ziqin; Ceder, Gerbrand
      Chemical Communications (Cambridge, United Kingdom) (2017), 53 (37), 5171-5174CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      We propose that Ti-contg. post-spinels may offer a practically-accessible route to fast multivalent ion diffusion in close-packed oxide lattices, with the caveat that substantial thermodn. driving forces for conversion reactions exist.
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    28. 28
      Dompablo, M. E. A.; Krich, C.; Nava-Avendaño, J.; Biškup, N.; Palacín, M. R.; Bardé, F. A joint computational and experimental evaluation of CaMn2O4 polymorphs as cathode materials for Ca ion batteries. Chem. Mater. 2016, 28, 6886– 6893,  DOI: 10.1021/acs.chemmater.6b02146
      28
      A Joint Computational and Experimental Evaluation of CaMn2O4 Polymorphs as Cathode Materials for Ca Ion Batteries
      Dompablo, M. Elena Arroyo-de; Krich, Christopher; Nava-Avendano, Jessica; Biskup, Neven; Palacin, M. Rosa; Barde, Fanny
      Chemistry of Materials (2016), 28 (19), 6886-6893CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      The identification of potential cathode materials is a must for the development of a new calcium-ion based battery technol. In this work, we have first explored the electrochem. behavior of marokite-CaMn2O4 but the exptl. attempts to deinsert Ca ion from this compd. failed. First-principles calcns. indicate that in terms of voltage and capacity, marokite-CaMn2O4 could sustain reversible Ca deinsertion reactions; half decalciation is predicted at an av. voltage of 3.7 V with a vol. variation of 6%. However, the calcd. barriers for Ca diffusion are too high (1 eV), in agreement with the obsd. difficulty to deinsert Ca ion from the marokite structure. We have extended the computational investigation to two other CaMn2O4 polymorphs, the spinel and the CaFe2O4 structural types. Full Ca extn. from these CaMn2O4 polymorphs is predicted at an av. voltage of 3.1 V, but with a large vol. variation of around 20%. Structural factors limiting Ca diffusion in the three polymorphs are discussed and confronted with a previous computational investigation of the virtual-spinel [Ca]T[Mn2]OO4. Regardless the potential interest of [Ca]T[Mn2]OO4 as cathode for Ca ion batteries, calcns. suggests that the synthesis of this compd. would hardly be feasible. The present results unravel the bottlenecks assocd. with the design of feasible intercalation Ca electrode materials, and allow proposing guidelines for future research.
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    29. 29
      Müller-Buschbaum, H. The crystal chemistry of AM2O4 oxometallates. J. Alloys Compd. 2003, 349, 49– 104,  DOI: 10.1016/S0925-8388(02)00925-8
      29
      The crystal chemistry of AM2O4 oxometallates
      Muller-Buschbaum, Hk.
      Journal of Alloys and Compounds (2003), 349 (1-2), 49-104CODEN: JALCEU; ISSN:0925-8388. (Elsevier Science B.V.)
      This review summarizes the crystal chem. of oxometallates AM2O4, which indicates that >50 individual structure types regarding the formulas AM2O4 or A2MO4 exist. The spectrum of reported structures includes spinels, spineloids, compds. with closed and interrupted octahedra layers, tunnel structures, as well as square-planar polygons and dumb-bells. Irregular polyhedra around large metal ions were estd. by calcns. of effective coordination nos. (ECoN). Calcns. of the Coulomb terms of the lattice energy (MAPLE) lead to the centers of stereochem. active lone pairs in AM2O4 compds. contg. s2 cations. The positions of lone pairs and their crystal chem. function are pointed out in the corresponding figures.
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    30. 30
      Akimoto, J.; Takei, H. Synthesis and crystal structure of NaTi2O4: a new mixed-valence sodium titanate. J. Solid State Chem. 1989, 79, 212– 217,  DOI: 10.1016/0022-4596(89)90268-5
      30
      Synthesis and crystal structure of NaTi2O4: a new mixed-valence sodium titanate
      Akimoto, J.; Takei, H.
      Journal of Solid State Chemistry (1989), 79 (2), 212-17CODEN: JSSCBI; ISSN:0022-4596.
      Needle-shaped, black NaTi2O4, crystals, prepd. by the thermal reaction of Na2O with Ti2O3 and TiO2, crystallize in the orthorhombic Ca ferrite-type structure, space group Pnam with a 9.2615(10), b 10.7357(7), c 2.9556(3) Å, Z = 4, R = 0.029 and Rw = 0.034 for 1856 obsd. reflections. The framework structure is built up from double rutile chains, and 2 types of Ti sites are randomly occupied by Ti3+ and Ti4+ ions.
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    31. 31
      Darriet, J.; Vidal, A. Les composés NaRu2O4 et NaFeRuO4. Structure cristalline de NaFeRuO4. Bull. Soc. Fr. Minéral Cristallogr. 1975, 98, 374– 377
      31
      NaRu2O4 (sodium ruthenate) and NaFeRuO4 (sodium iron ruthenate) phases. Crystal structure of NaFeRuO4 (sodium iron ruthenate)
      Darriet, Jacques; Vidal, Alain
      Bulletin de la Societe Francaise de Mineralogie et de Cristallographie (1975), 98 (6), 374-7CODEN: BUFCAE; ISSN:0037-9328.
      NaRu2O4 and NaFeRuO4 crystd. in the orthorhombic system, isotypic with CaFe2O (NaRu2O4 a 9.265, b 2.821, c 11.159 Å; NaFeRuO4 a 9.218, b 2.956, c 10.848 Å). Single-crystal x-ray structure detn. of NaFeRuO4 shows that Fe and Ru atoms are randomly distributed between both independent crystallog. sites.
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    32. 32
      Viciu, L.; Ryser, A.; Mensing, C.; Bos, J.-W. G. Ambient-pressure synthesis of two new vanadium-based calcium ferrite-type compounds: NaV1.25Ti0.75O4 and NaVSnO4. Inorg. Chem. 2015, 54, 7264– 7271,  DOI: 10.1021/acs.inorgchem.5b00655
      32
      Ambient-Pressure Synthesis of Two New Vanadium-Based Calcium Ferrite-Type Compounds: NaV1.25Ti0.75O4 and NaVSnO4
      Viciu, Liliana; Ryser, Alice; Mensing, Christian; Bos, Jan-Willem G.
      Inorganic Chemistry (2015), 54 (15), 7264-7271CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Two new CaFe2O4-type compds. NaV1.25Ti0.75O4 (1) and NaVSnO4 (2) were prepd. at ambient pressure and temps. < 800°. This contrasts with the parent material NaV2O4 which was synthesized at 6 GPa and 1300°. The lattice parameters are a 9.1500(4), b 2.9399(3), and c 10.6568(5) Å for 1 and a 9.3083(6), b 3.0708(2), and c 10.9194(5) Å for 2 (space group Pnma). Crystallog. data and at. coordinates are given. Structure refinement against neutron powder diffraction data reveals that V/Ti and V/Sn are disordered over two octahedral sites. Both materials were characterized by a magnetic transition near 150 K below which the Curie moment is reduced from a value consistent with V3+ [0.75 emu molV-1 K-1 for 1 and 0.58 emu molV-1 K-1 for 2] to 0.23 emu molV-1 K-1 for 1 and 0.30 emu molV-1 K-1 for 2, signaling a 70-50% redn. in the paramagnetic moment. The Weiss temp. (θ) is reduced from -285(1) and -138 K (2) to values close to 0 K, suggesting that the remaining spins are dil. and weakly interacting. Heat capacity measurements reveal a gradual loss of magnetic entropy between 2 and 150 K, consistent with short-range bulk magnetic ordering. Heat capacity and magnetic susceptibility measurements reveal a no. of weak magnetic transitions <6 K involving both antiferromagnetic and ferromagnetic components.
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    33. 33
      Akimoto, J.; Awaka, J.; Kijima, N.; Takahashi, Y.; Maruta, Y.; Tokiwa, K.; Watanabe, T. High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure. J. Solid State Chem. 2006, 179, 169– 174,  DOI: 10.1016/j.jssc.2005.10.020
      33
      High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure
      Akimoto, Junji; Awaka, Junji; Kijima, Norihito; Takahashi, Yasuhiko; Maruta, Yuichi; Tokiwa, Kazuyasu; Watanabe, Tsuneo
      Journal of Solid State Chemistry (2006), 179 (1), 169-174CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
      Single crystals of a new Na Mn oxide, NaMn2O4, were synthesized for the 1st time using a high-temp. and high-pressure technique. The NaMn2O4 single crystal is black, has a needle shape, and crystallizes in the orthorhombic Ca ferrite-type structure, space group Pnam with a 8.9055(18), b 11.0825(22), c 2.8524(5) Å, and Z = 4. The structure was detd. from a single-crystal x-ray study and refined to the conventional values R = 0.041 and Rw = 0.034 for 1190 obsd. reflections. Crystallog. data and at. coordinates are given. The framework structure is built up from edge-sharing chains of MnO6 octahedra that condense to form 1-dimensional tunnels in which the Na atoms are located. The Mn-O bond distance and bond valence analyses revealed the Mn valence Mn3+/Mn4+ ordering in the two double rutile chains of NaMn2O4.
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    34. 34
      Yamaura, K.; Huang, Q.; Moldovan, M.; Young, D. P.; Sato, A.; Baba, Y.; Nagai, T.; Matsui, Y.; Takayama-Muromachi, E. High-pressure synthesis, crystal structure determination, and a Ca substitutional study of the metallic rhodium oxide NaRh2O4. Chem. Mater. 2005, 17, 359– 365,  DOI: 10.1021/cm0483846
      34
      High-Pressure Synthesis, Crystal Structure Determination, and a Ca Substitution Study of the Metallic Rhodium Oxide NaRh2O4
      Yamaura, Kazunari; Huang, Qingzhen; Moldovan, Monica; Young, David P.; Sato, Akira; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Takayama-Muromachi, Eiji
      Chemistry of Materials (2005), 17 (2), 359-365CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      The sodium rhodate NaRh2O4 was synthesized for the first time and characterized by neutron and x-ray diffraction studies and measurements of magnetic susceptibility, sp. heat, elec. resistivity, and the Seebeck coeff. NaRh2O4 crystallizes in the CaFe2O4-type structure, which is comprised of a characteristic RhO6 octahedral network. The compd. is metallic in nature, probably reflecting the 1:1 mixed valence character of Rh(III) and Rh(IV) in the network. For further studies of the compd., the Rh valence was varied significantly by an aliovalent substitution: the full-range solid soln. between NaRh2O4 and CaRh2O4 was achieved and characterized as well. The metallic state was dramatically altered, and a peculiar magnetism developed in the low Na concn. range.
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    35. 35
      Shukaev, I. L.; Volochaev, V. A. Ternary sodium and titanium oxides with cobalt(II). Russ. J. Inorg. Chem. 1995, 12, 1974– 1980
      There is no corresponding record for this reference.
    36. 36
      Nalbandyan, V. B.; Shukaev, I. L. Triple oxides of sodium, nickel, and titanium. Russ. J. Inorg. Chem. 1992, 37, 1231– 1235
      There is no corresponding record for this reference.
    37. 37
      Archaimbault, F.; Choisnet, J.; Rautureau, M. New ferriantimonates with the CaFe2O4 type structure: Na2Fe3SbO8 and isomorphous series Na2Fe2+xSn2–2xSbxO8 (0 ≤ x ≤ 1). Eur. J. Solid State Inorg. Chem. 1988, 25, 573– 587
      There is no corresponding record for this reference.
    38. 38
      Ishiguro, T.; Tanaka, K.; Marumo, F.; Ismail, M. G. M. U.; Hirano, S.; Somiya, S. Non-stoichiometric sodium iron (II) titanium (IV) oxide. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1978, 34, 3346– 3348,  DOI: 10.1107/S0567740878010870
      There is no corresponding record for this reference.
    39. 39
      Feger, C. R.; Kolis, J. W. Na3Mn4Te2O12. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1998, 54, 1055– 1057,  DOI: 10.1107/S0108270197020076
      39
      Na3Mn4Te2O12
      Feger, Christopher R.; Kolis, Joseph W.
      Acta Crystallographica, Section C: Crystal Structure Communications (1998), C54 (8), 1055-1057CODEN: ACSCEE; ISSN:0108-2701. (Munksgaard International Publishers Ltd.)
      The title compd., Na Mn tellurate, was obtained by hydrothermal synthesis and adopts a super-structure related to the CaFe2O4 structure type, with the Mn and Te atoms ordered along the b axis (short axis in the CaFe2O4 structure). Electron-counting schemes show that this compd. is a mixed-valence MnII/MnIII compd., and bond valence sums were used to suggest that there is no site preference for the higher charged Mn atom. Crystallog. data are given.
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    40. 40
      Toby, B. H.; Von Dreele, R. B. GSAS-II: the genesis of a modern open-source all purpose crystallography software package. J. Appl. Crystallogr. 2013, 46, 544– 549,  DOI: 10.1107/S0021889813003531
      40
      GSAS-II: the genesis of a modern open-source all purpose crystallography software package
      Toby, Brian H.; Von Dreele, Robert B.
      Journal of Applied Crystallography (2013), 46 (2), 544-549CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      The newly developed GSAS-II software is a general purpose package for data redn., structure soln. and structure refinement that can be used with both single-crystal and powder diffraction data from both neutron and x-ray sources, including lab. and synchrotron sources, collected on both two- and 1-dimensional detectors. It is intended that GSAS-II will eventually replace both the GSAS and the EXPGUI packages, as well as many other utilities. GSAS-II is open source and is written largely in object-oriented Python but offers speeds comparable to compiled code because of its reliance on the Python NumPy and SciPy packages for computation. It runs on all common computer platforms and offers highly integrated graphics, both for a user interface and for interpretation of parameters. The package can be applied to all stages of crystallog. anal. for const.-wavelength x-ray and neutron data. Plans for considerable addnl. development are discussed.
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    41. 41
      Amoureux, J.-P.; Fernandez, C.; Steuernagel, S. Z Filtering in MQMAS NMR. J. Magn. Reson., Ser. A 1996, 123, 116– 118,  DOI: 10.1006/jmra.1996.0221
      41
      Z filtering in MQMAS NMR
      Amoureux, Jean-Paul; Fernandez, Christian; Steuernageel, Stefan
      Journal of Magnetic Resonance, Series A (1996), 123 (1), 116-118CODEN: JMRAE2; ISSN:1064-1858. (Academic)
      A Z-filtering method is applied to MQMAS NMR which greatly improves the efficiency of the method. This approach was used to analyze the 27Al 3QMAS NMR spectrum of AlPO-14.
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    42. 42
      Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
      42
      Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
      Kresse, G.; Furthmuller, J.
      Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
      The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
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    43. 43
      Kresse, G.; Hafner, J. Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements. J. Phys.: Condens. Matter 1994, 6, 8245,  DOI: 10.1088/0953-8984/6/40/015
      43
      Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements
      Kresse, G.; Hafner, J.
      Journal of Physics: Condensed Matter (1994), 6 (40), 8245-57CODEN: JCOMEL; ISSN:0953-8984.
      The construction of accurate pseudopotentials with good convergence properties for the first-row and transition elements is discussed. By combining an improved description of the pseudo-wavefunction inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence can be achieved. With the new pseudopotentials, basis sets with no more than 75-100 plane waves per atom are sufficient to reproduce the results obtained with the most accurate norm-conserving pseudopotentials.
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    44. 44
      Blöchl, P. E.; Jepsen, O.; Andersen, O. K. Improved tetrahedron method for Brillouin-zone integrations. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 49, 16223,  DOI: 10.1103/PhysRevB.49.16223
      44
      Improved tetrahedron method for Brillouin-zone integrations
      Blochl, Peter E.; Jepsen, O.; Andersen, O. K.
      Physical Review B: Condensed Matter and Materials Physics (1994), 49 (23), 16223-33CODEN: PRBMDO; ISSN:0163-1829.
      Several improvements of the tetrahedron method for Brillouin-zone integrations are presented. (1) A translational grid of k points and tetrahedra is suggested that renders the results for insulators identical to those obtained with special-point methods with the same no. of k points. (2) A simple correction formula goes beyond the linear approxn. of matrix elements within the tetrahedra and also improves the results for metals significantly. For a required accuracy this reduces the no. of k points by orders of magnitude. (3) Irreducible k points and tetrahedra are selected by a fully automated procedure, requiring as input only the space-group operations. (4) The integration is formulated as a weighted sum over irreducible k points with integration wts. calcd. using the tetrahedron method once for a given band structure. This allows an efficient use of the tetrahedron method also in plane-wave-based electronic-structure methods.
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    45. 45
      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
      45
      Generalized gradient approximation made simple
      Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
      Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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    46. 46
      Wang, L.; Maxisch, T.; Ceder, G. Oxidation energies of transition metal oxides within the GGA+U framework. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 195107,  DOI: 10.1103/PhysRevB.73.195107
      46
      Oxidation energies of transition metal oxides within the GGA+U framework
      Wang, Lei; Maxisch, Thomas; Ceder, Gerbrand
      Physical Review B: Condensed Matter and Materials Physics (2006), 73 (19), 195107/1-195107/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      The energy of a large no. of oxidn. reactions of 3d transition metal oxides is computed using the generalized gradient approach (GGA) and GGA+U methods. Two substantial contributions to the error in GGA oxidn. energies are identified. The first contribution originates from the overbinding of GGA in the O2 mol. and only occurs when the oxidant is O2. The second error occurs in all oxidn. reactions and is related to the correlation error in 3d orbitals in GGA. Strong self-interaction in GGA systematically penalizes a reduced state (with more d electrons) over an oxidized state, resulting in an overestimation of oxidn. energies. The const. error in the oxidn. energy from the O2 binding error can be cor. by fitting the formation enthalpy of simple nontransition metal oxides. Removal of the O2 binding error makes it possible to address the correlation effects in 3d transition metal oxides with the GGA+U method. Calcd. oxidn. energies agree well with exptl. data for reasonable and consistent values of U.
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    47. 47
      Jain, A.; Ong, S. P.; Hautier, G.; Chen, W.; Richards, W. D.; Dacek, S.; Cholia, S.; Gunter, D.; Skinner, D.; Ceder, G.; Persson, K. A. Commentary: The Materials Project: A materials genome approach to accelerating materials innovation. APL Mater. 2013, 1, 011002,  DOI: 10.1063/1.4812323
      47
      Commentary: The Materials Project: A materials genome approach to accelerating materials innovation
      Jain, Anubhav; Ong, Shyue Ping; Hautier, Geoffroy; Chen, Wei; Richards, William Davidson; Dacek, Stephen; Cholia, Shreyas; Gunter, Dan; Skinner, David; Ceder, Gerbrand; Persson, Kristin A.
      APL Materials (2013), 1 (1), 011002/1-011002/11CODEN: AMPADS; ISSN:2166-532X. (American Institute of Physics)
      Accelerating the discovery of advanced materials is essential for human welfare and sustainable, clean energy. In this paper, we introduce the Materials Project (www.materialsproject.org), a core program of the Materials Genome Initiative that uses high-throughput computing to uncover the properties of all known inorg. materials. This open dataset can be accessed through multiple channels for both interactive exploration and data mining. The Materials Project also seeks to create open-source platforms for developing robust, sophisticated materials analyses. Future efforts will enable users to perform rapid-prototyping'' of new materials in silico, and provide researchers with new avenues for cost-effective, data-driven materials design. (c) 2013 American Institute of Physics.
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    48. 48
      Jain, A.; Hautier, G.; Ong, S. P.; Moore, C. J.; Fischer, C. C.; Persson, K. A.; Ceder, G. Formation enthalpies by mixing GGA and GGA + U calculations. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 84, 045115,  DOI: 10.1103/PhysRevB.84.045115
      48
      Formation enthalpies by mixing GGA and GGA + U calculations
      Jain, Anubhav; Hautier, Geoffroy; Ong, Shyue Ping; Moore, Charles J.; Fischer, Christopher C.; Persson, Kristin A.; Ceder, Gerbrand
      Physical Review B: Condensed Matter and Materials Physics (2011), 84 (4), 045115/1-045115/10CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      Std. approxns. to the d. functional theory exchange-correlation functional have been extraordinarily successful, but calcg. formation enthalpies of reactions involving compds. with both localized and delocalized electronic states remains challenging. In this work the authors examine the shortcomings of the generalized gradient approxn. (GGA) and GGA + U in accurately characterizing such difficult reactions. They then outline a methodol. that mixes GGA and GGA + U total energies (using known binary formation data for calibration) to more accurately predict formation enthalpies. For a test set of 49 ternary oxides, this methodol. can reduce the mean abs. relative error in calcd. formation enthalpies from approx. 7.7-21% in GGA + U to under 2%. As another example, the authors show that neither GGA nor GGA + U alone accurately reproduces the Fe-P-O phase diagram; however, the mixed methodol. successfully predicts all known phases as stable by naturally stitching together GGA and GGA + U results. As a final example, this technique was applied to the calcn. of the Li-conversion voltage of LiFeF3. These results indicate that mixing energies of several functionals represents one avenue to improve the accuracy of total energy computations without affecting the cost of calcn.
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    49. 49
      Ong, S. P.; Richards, W. D.; Jain, A.; Hautier, G.; Kocher, M.; Cholia, S.; Gunter, D.; Chevrier, V. L.; Persson, K. A.; Ceder, G. Python Materials Genomics (pymatgen): A robust, open-source python library for materials analysis. Comput. Mater. Sci. 2013, 68, 314– 319,  DOI: 10.1016/j.commatsci.2012.10.028
      49
      Python Materials Genomics (pymatgen): A robust, open-source python library for materials analysis
      Ong, Shyue Ping; Richards, William Davidson; Jain, Anubhav; Hautier, Geoffroy; Kocher, Michael; Cholia, Shreyas; Gunter, Dan; Chevrier, Vincent L.; Persson, Kristin A.; Ceder, Gerbrand
      Computational Materials Science (2013), 68 (), 314-319CODEN: CMMSEM; ISSN:0927-0256. (Elsevier B.V.)
      We present the Python Materials Genomics (pymatgen) library, a robust, open-source Python library for materials anal. A key enabler in high-throughput computational materials science efforts is a robust set of software tools to perform initial setup for the calcns. (e.g., generation of structures and necessary input files) and post-calcn. anal. to derive useful material properties from raw calcd. data. The pymatgen library aims to meet these needs by (1) defining core Python objects for materials data representation, (2) providing a well-tested set of structure and thermodn. analyses relevant to many applications, and (3) establishing an open platform for researchers to collaboratively develop sophisticated analyses of materials data obtained both from first principles calcns. and expts. The pymatgen library also provides convenient tools to obtain useful materials data via the Materials Project's REpresentational State Transfer (REST) Application Programming Interface (API). As an example, using pymatgen's interface to the Materials Project's RESTful API and phase diagram package, we demonstrate how the phase and electrochem. stability of a recently synthesized material, Li4SnS4, can be analyzed using a min. of computing resources. We find that Li4SnS4 is a stable phase in the Li-Sn-S phase diagram (consistent with the fact that it can be synthesized), but the narrow range of lithium chem. potentials for which it is predicted to be stable would suggest that it is not intrinsically stable against typical electrodes used in lithium-ion batteries.
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    50. 50
      Avdeev, M. Yu; Nalbandyan, V. B.; Medvedev, B. S. Hexagonal sodium titanate chromite: a new high-conductivity solid electrolyte. Inorg. Mater. 1997, 33, 500– 503
      50
      Hexagonal sodium titanate chromite: a new high-conductivity solid electrolyte
      Avdeev, M. Yu.; Nalbandyan, V. B.; Medvedev, B. S.
      Inorganic Materials (Translation of Neorganicheskie Materialy) (1997), 33 (5), 500-503CODEN: INOMAF; ISSN:0020-1685. (MAIK Nauka/Interperiodica)
      NaxCrxTi1-xO2, a new nonstoichiometric hexagonal layered phase with high sodium ion cond., was prepd. by solid-state reaction in a controlled atm. Its stability field was outlined, the lattice parameters calcd., and the crystal chem. of cation cond. was discussed.
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    51. 51
      Mumme, W. G.; Reid, A. F. Non-stoichiometric sodium iron titanate, NaxFexTi2-xO4, 0.90> x> 0.75. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1968, 24, 625– 631,  DOI: 10.1107/S0567740868002955
      51
      Non-stoichiometric sodium iron titanate, Na(sub x)Fe(sub x)Ti(sub 2-x)O4, 0.90>x>0.75
      Mumme, W. G.; Reid, A. F.
      Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1968), 24 (Pt. 5), 625-31CODEN: ACBCAR; ISSN:0567-7408.
      The new, congruently melting compd. NaxFexTi2-xO4, 0.90 > x > 0.75, was prepd. as a powder at 1000° and in the cryst. form by melting NaFeTiO4 in air at 1220°. It is orthorhombic, space group Pnma, with unit-cell dimensions a 9.248, b 2.973, and c 11.344 A. at the compn. x = 0.90. The Fe and Ti atoms randomly occupy octahedral positions, and the octahedra within a unit cell are joined by extensive edge-sharing into Z-shaped groups of 4. These groups extend in infinite ribbons in the b-axis direction, and are corner joined to each other, thereby providing double tunnels of Na-ion sites, not all occupied. The structure is a rearrangement, with a necessary Na loss, of the limiting compn. NaFeTiO4, which is a CaFe2O4 isotype with similar crystallographic consts., but contg. pairs of edge-shared octahedra corner joined to form single tunnels for Na ions.
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    52. 52
      Nalbandyan, V. B.; Rykalova, S. I.; Bikyashev, E. A.; Isakova, S. Yu Sodium titanium magnesium (zinc) ternary oxides. Zh. Neorg. Khim. 1989, 34, 2381– 2386
      52
      Ternary oxides of sodium, titanium and magnesium or zinc
      Nalbandyan, V. B.; Rykalova, S. I.; Bikyashev, E. A.; Isakova, S. Yu.
      Zhurnal Neorganicheskoi Khimii (1989), 34 (9), 2381-6CODEN: ZNOKAQ; ISSN:0044-457X.
      Subsolidus phase equil. was studied in the Na8Ti5O14-TiO2-ZnO(MgO) systems at 900-1100°. Crystn. from melts or from molten NaF was studied for MgO compns. Ten ternary oxides and 1 oxyfluoride were identified. Their structures are related to NaTi-bronzes, nonstoichiometric Na ferrititanate, α-NaFeO2, Na4Ti5O12, and 4 new structure types. The crystallochem. of these compds. is discussed.
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    53. 53
      Shukaev, I. L.; Butova, V. V.; Chernenko, S. V.; Pospelov, A. A.; Shapovalov, V. V.; Guda, A. A.; Aboraia, A. M.; Zahran, H. Y.; Yahia, I. S.; Soldatov, A. V. New orthorhombic sodium iron(+2) titanate. Ceram. Int. 2020, 46, 4416– 4422,  DOI: 10.1016/j.ceramint.2019.10.167
      53
      New orthorhombic sodium iron(+2) titanate
      Shukaev, Igor L.; Butova, Vera V.; Chernenko, Sergey V.; Pospelov, Andrey A.; Shapovalov, Victor V.; Guda, Alexander A.; Aboraia, Abdelaziz M.; Zahran, Heba Y.; Yahia, Ibrahim S.; Soldatov, Alexander V.
      Ceramics International (2020), 46 (4), 4416-4422CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
      The set of compns. with Fe2+ in the system NaxFex/2Ti2-x/2O4 has been prepd. by solid-state reactions in the inert atm. at 1050 °C. The oxidn. state of iron was confirmed using the XANES method. Na0.88Fe0.44Ti1.56O4 is the new four-element compd. in Na2O-"FeO"-TiO2 system. According to the X-ray powder data, it is orthorhombic, Pnma, a = 9.3624(1), b = 2.96718(4), c = 11.3435(1) Å and has the same structure as Na0.9Fe0.9Ti1.1O4 with Fe3+. The structure was refined by the Rietveld method. The 3D-framework of (Fe, Ti)O6 octahedra contains quadruple rutile-like chains and sodium ions in double tunnels. Fe/Ti partial ordering in the framework and sodium distribution in the tunnels were studied addnl. using the method of bond valence sums and Voronoi tessellation. The structure and compn. of Na0.88Fe0.44Ti1.56O4 make it a promising material for cathode application.
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    54. 54
      Thackeray, M. M.; de Kock, A.; Rossouw, M. H.; Liles, D.; Bittihn, R.; Hoge, D. Spinel electrodes from the Li-Mn-O system for rechargeable lithium battery applications. J. Electrochem. Soc. 1992, 139, 363– 366,  DOI: 10.1149/1.2069222
      54
      Spinel electrodes from the lithium-manganese-oxygen system for rechargeable lithium battery applications
      Thackeray, M. M.; De Kock, A.; Rossouw, M. H.; Liles, D.; Bittihn, R.; Hoge, D.
      Journal of the Electrochemical Society (1992), 139 (2), 363-6CODEN: JESOAN; ISSN:0013-4651.
      The electrochem. and structural properties of spinel phases in the Li-Mn-O system are discussed as insertion electrodes for rechargeable lithium batteries. The performance of button-type cells contg. electrodes from the Li2O yMnO2 system, e.g., the stoichiometric spinel Li4Mn5O12 (y = 2.5) and the defect spinel Li2Mn4O9 (y = 4.0), is highlighted and compared with a cell contg. a std. LiMn2O4 spinel electrode.
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    55. 55
      Deschanvres, A.; Raveau, B.; Sekkal, Z. Mise en evidence et etude cristallographique d’une nouvelle solution solide de type spinelle Li1+xTi2–xO4 0 ⩽ x ⩽ 0, 333. Mater. Res. Bull. 1971, 6, 699– 704,  DOI: 10.1016/0025-5408(71)90103-6
      55
      Demonstration and crystallographic study of new spinel-type solid solution Li1+xTi1-3xTi1+2xO4 with O .leq. .tim. .leq. 0.33
      Deschanvres, A.; Raveau, B.; Sekkal, Z.
      Materials Research Bulletin (1971), 6 (8), 699-704CODEN: MRBUAC; ISSN:0025-5408.
      A new solid-soln. spinel type Li1+xTi3+1-3x-Ti4+1+2xO4 with O ≤ x ≤ 0.33 has been isolated. The positions of the different atoms in the cubic cell were detd.
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    56. 56
      Rickert, K.; Sedefoglu, N.; Malo, S.; Caignaert, V.; Kavak, H.; Poeppelmeier, K. R. Structural, electrical, and optical properties of the tetragonal, fluorite-related Zn0.456In1.084Ge0.460O3. Chem. Mater. 2015, 27, 5072– 5079,  DOI: 10.1021/acs.chemmater.5b01724
      56
      Structural, Electrical, and Optical Properties of the Tetragonal, Fluorite-Related Zn0.456In1.084Ge0.460O3
      Rickert, Karl; Sedefoglu, Nazmi; Malo, Sylvie; Caignaert, Vincent; Kavak, Hamide; Poeppelmeier, Kenneth R.
      Chemistry of Materials (2015), 27 (14), 5072-5079CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      We report the discovery of Zn0.456In1.084Ge0.460O3, a material closely related to bixbyite. In contrast, however, the oxygen atoms in this new phase occupy 4 Wyckoff positions, which result in 4 four-coordinate, 24 six-coordinate (2 different Wyckoff positions), and 4 eight-coordinate sites as compared to the 32 six-coordinate (also 2 different Wyckoff positions) sites of bixbyite. This highly ordered material is related to fluorite, Ag6GeSO8, and γ-UO3 and is n-type with a bulk carrier concn. of 4.772 × 1014 cm-3. The reduced form displays an av. room temp. cond. of 99(11) S·cm-1 and an av. optical band gap of 2.88(1) eV. These properties are comparable to those of In2O3, which is the host material for the current leading transparent conducting oxides. The structure of Zn0.456In1.084Ge0.460O3 is solved from a combined refinement of synchrotron X-ray powder diffraction and time-of-flight neutron powder diffraction and confirmed with electron diffraction. The soln. is a new, layered, tetragonal structure in the I41/amd space group with a = 7.033986(19) Å and c = 19.74961(8) Å. The complex cationic topol. network adopted by Zn0.456In1.084Ge0.460O3 offers the potential for future studies to further understand carrier generation in ∼3 eV oxide semiconductors.
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    57. 57
      Marinkovic, B. A.; Mancic, L.; Jardim, P. M.; Milosevic, O.; Rizzo, F. Hydrothermal synthesis of NaxFexTi2-xO4 from natural ilmenite sand: a CaFe2O4 structure type compound. Solid State Commun. 2008, 145, 346– 350,  DOI: 10.1016/j.ssc.2007.12.006
      57
      Hydrothermal synthesis of NaxFexTi2-xO4 from natural ilmenite sand: A CaFe2O4 structure type compound
      Marinkovic, B. A.; Mancic, L.; Jardim, P. M.; Milosevic, O.; Rizzo, F.
      Solid State Communications (2008), 145 (7-8), 346-350CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)
      NaxFexTi2-xO4, a compd. with CaFe2O4-type structure, was obtained via hydrothermal route at <200°C. Natural ilmenite sand, a low cost reagent, was used as a precursor and reacted with 10 mol/L NaOH for 70 h to obtained high yield (92% wt) of NaxFexTi2-xO4 with x = 0.76-0.79 , as evaluated through the Rietveld refinement and quant. phase anal. of X-ray powder diffraction data. TEM showed that NaxFexTi2-xO4 appears in submicron to micron crystals with well-defined facets, growing along the [001] crystallog. direction, which means that the tunnels, a peculiarity of this crystal structure, are oriented along the direction of growth.
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    58. 58
      Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751– 767,  DOI: 10.1107/S0567739476001551
      There is no corresponding record for this reference.
    59. 59
      Mumme, W. G. The structure of Na4Mn4Ti5O18. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1968, 24, 1114– 1120,  DOI: 10.1107/S0567740868003778
      59
      Structure of Na4Mn4Ti5O18
      Mumme, W. G.
      Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1968), 24 (Pt. 8), 1114-20CODEN: ACBCAR; ISSN:0567-7408.
      Na4Mn4Ti5O18, formed at 1200° by crystn. from the compn. NaMnTiO4, is orthorhombic, with unit-cell dimensions a 9.268, b 26.601, c 2.888 A. Mn3+ and Ti4+ atoms occupy octahedral positions, while the coordination of another Mn3+ is a rectangular pyramid. In this structure, groups of octahedra, joined by extensive edge and corner sharing, are linked together by the 5-coordinated Mn3+ to leave a series of tunnels for the Na ions. One of these is a single tunnel similar to that found in Ca ferrite; the other is a much larger one and contains sites for 4 Na ions, only half of which are filled. The chem. compn. was deduced from this structure anal.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXksFGitrk%253D&md5=8e4dd7512a9f1507c527a464118c38e0
    60. 60
      Parant, J.-P.; Olazcuaga, R.; Devalette, M.; Fouassier, C.; Hagenmuller, P. Sur quelques nouvelles phases de formule NaxMnO2 (x ≤ 1). J. Solid State Chem. 1971, 3, 1– 11,  DOI: 10.1016/0022-4596(71)90001-6
      60
      New phases of the formula NaxMnO2(x.leq.1)
      Parant, Jean P.; Olazcuaga, Roger; Devalette, Michel; Fouassier, Claude; Hagenmuller, Paul
      Journal of Solid State Chemistry (1971), 3 (1), 1-11CODEN: JSSCBI; ISSN:0022-4596.
      Several new ternary oxides have been isolated in the Mn-O-Na system for Na/Mn ≤ 1: Na0.20MnO2, Na0.40-MnO2, Na0.44MnO2, Na0.70MnO2+y(0 ≤ y ≤ 0.25), and NaMnO2. All structures are characterized by edge sharing (MnO6) octahedra, forming double or triple chains for small Na contents and 2-dimensional layers when the Na/Mn ratio becomes close to 1. Elec. and magnetic behavior of the phases has been detd.
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    61. 61
      Toda, K.; Kameo, Y.; Kurita, S.; Sato, M. Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO4 (Ln = rare earth). J. Alloys Compd. 1996, 234, 19– 25,  DOI: 10.1016/0925-8388(95)01969-3
      61
      Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO4 (Ln = rare earth)
      Toda, Kenji; Kameo, Yutaka; Kurita, Satoru; Sato, Mineo
      Journal of Alloys and Compounds (1996), 234 (1), 19-25CODEN: JALCEU; ISSN:0925-8388. (Elsevier)
      The layered perovskite compds. NaLnTiO4 (Ln = rare earth element; LaNaTiO4, PrNaTiO4, NdNaTiO4, SmNaTiO4, EuNaTiO4, GdNaTiO4, YNaTiO4 and LuNaTiO4) were synthesized by the solid state reaction. The crystal structure of these compds. were detd. by the Rietveld anal. Single phases of the compds. (except for Ln = Lu) could be prepd. only under very restricted prepn. conditions. The compn. of NaLuTiO4 was not a single phase under the conditions employed in this study. Compds. NaLnTiO4 have a tetragonal symmetry for Ln = La-Nd, while an orthorhombic symmetry is obsd. for Ln = Sm-Lu. The stabilization of NaLnTiO4 is discussed on the basis of the relative sizes of the rare earth and the alkali metal ions. The lowering of the symmetry is considered to be introduced by the mismatch between TiO2 and LnO2 layers. Ionic conductivities attributed to the interlayer sodium ions were obsd. at high temps. The magnitude of ionic cond. of NaLaTiO4, with a single perovskite layer, was much higher than that of Na2La2Ti3O10, with a triple perovskite layer. This high ionic cond. is due to the weak interaction between the perovskite layer and interlayer sodium ions.
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    62. 62
      Bruhn, G.; Beutel, S.; Pfaff, G.; Albert, B. Low-temperature synthesis of freudenbergite-type titanate bronzes from metal halides, crystal growth from molybdate flux, and crystal structure determination of Na1.84Zn0.92Ti7.08O16. J. Alloys Compd. 2015, 644, 783– 787,  DOI: 10.1016/j.jallcom.2015.05.076
      62
      Low-temperature synthesis of freudenbergite-type titanate bronzes from metal halides, crystal growth from molybdate flux, and crystal structure determination of Na1.84Zn0.92Ti7.08O16
      Bruhn, Gerd; Beutel, Sebastian; Pfaff, Gerhard; Albert, Barbara
      Journal of Alloys and Compounds (2015), 644 (), 783-787CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      A new pptn. method to synthesize freudenbergite-type phases from metal halides was developed, and titanate bronzes NaxMyTi8-yO16 with M = Fe, Zn were obtained as micro-cryst. powders. The crystal structures were refined based on synchrotron x-ray data using the Rietveld method. Single crystals of the new compd. Na1.848(8)Zn0.924(3)Ti7.076(3)O16 were grown from molybdate flux, and its crystal structure was detd. (space group C2/m, a 1230.2(2), b 381.94(4), c 650.2(2) pm, and β 107.09(2)°). Crystallog. data and at. coordinates are given. It is isostructural to the Fe-contg. freudenbergite-type phase. Absorption spectra from diffuse reflection measurements are shown.
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    63. 63
      Kunz, M.; Brown, I. D. Out-of-center distortions around octahedrally coordinated d0 transition metals. J. Solid State Chem. 1995, 115, 395– 406,  DOI: 10.1006/jssc.1995.1150
      63
      Out-of-center distortions around octahedrally coordinated d0 transition metals
      Kunz, Martin; Brown, I. David
      Journal of Solid State Chemistry (1995), 115 (2), 395-406CODEN: JSSCBI; ISSN:0022-4596. (Academic)
      The bond valence growth approach was used to model the characteristic out-of-center electronic distortions around d0 transition model cations in octahedral coordination. The distortions are influenced not only by the electronic structure of the cation but also by the structure of the bond network, by lattice incommensurations, and by cation-cation repulsion. These latter effects often det. whether a distortion will occur and, if so, in what direction. Once the direction of an expected out-of-center distortion is known, its magnitude can be modeled using modified bond valence network equations, where certain bonds are weighted to take into account the intrinsic inequality of the bonds in such a distorted coordination. The arguments are illustrated by examples.
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    64. 64
      Ok, K. M.; Halasyamani, P. S.; Casanova, D.; Llunell, M.; Alemany, P.; Alvarez, S. Distortions in octahedrally coordinated d0 transition metal oxides: a continuous symmetry measures approach. Chem. Mater. 2006, 18, 3176– 3183,  DOI: 10.1021/cm0604817
      64
      Distortions in Octahedrally Coordinated d0 Transition Metal Oxides: A Continuous Symmetry Measures Approach
      Ok, Kang Min; Halasyamani, P. Shiv; Casanova, David; Llunell, Miquel; Alemany, Pere; Alvarez, Santiago
      Chemistry of Materials (2006), 18 (14), 3176-3183CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      More than 750 d0 transition metal oxide octahedra were examd. to better understand the out-of-center distortion occurring with these cations. A continuous symmetry measures approach was used to quantify the magnitude and direction of the distortion. Using this approach the authors were able to divide the d0 transition metals into three categories: strong (Mo6+ and V5+), moderate (W6+, Ti4+, Nb5+, and Ta5+), and weak (Zr4+ and Hf4+) distorters. The authors also examd. and discussed the directional preference of the distortion for each cation.
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    65. 65
      Urban, A.; Abdellahi, A.; Dacek, S.; Artrith, N.; Ceder, G. Electronic-structure origin of cation disorder in transition-metal oxides. Phys. Rev. Lett. 2017, 119, 176402,  DOI: 10.1103/PhysRevLett.119.176402
      65
      Electronic-structure origin of cation disorder in transition-metal oxides
      Urban, Alexander; Abdellahi, Aziz; Dacek, Stephen; Artrith, Nongnuch; Ceder, Gerbrand
      Physical Review Letters (2017), 119 (17), 176402/1-176402/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
      Cation disorder is an important design criterion for technol. relevant transition-metal (TM) oxides, such as radiation-tolerant ceramics and Li-ion battery electrodes. In this Letter, we use a combination of first-principles calcns., normal mode anal., and band-structure arguments to pinpoint a specific electronic-structure effect that influences the stability of disordered phases. We find that the electronic configuration of a TM ion dets. to what extent the structural energy is affected by site distortions. This mechanism explains the stability of disordered phases with large ionic radius differences and provides a concrete guideline for the discovery of novel disordered compns.
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    66. 66
      Shilov, G. V.; Atovmyan, L. O.; Volochaev, V. A.; Nalbandyan, V. B. Crystal structure and ionic conductivity of a new sodium magnesium titanium oxide. Kristallografiya 1999, 44, 1029– 1033
      66
      Crystal structure and ionic conductivity of a new sodium magnesium titanium oxide
      Shilov, G. V.; Atovmyan, L. O.; Volochaev, V. A.; Nalbandyan, V. B.
      Kristallografiya (1999), 44 (6), 1029-1033CODEN: KRISAJ; ISSN:0023-4761. (MAIK Nauka/Interperiodica Publishing)
      By solid-phase synthesis and crystn. from the melt a nonstoichiometric phase Na4+2x(MgxTi8-x)O18 (x = 0.76) was obtained. Crystals are monoclinic, space group B2/m, with a 23.063(8), b 10.689(4), c 2.944(2) Å , and γ 76.40(4)°; Z = 2; R = 0.0506 for 2679 reflections. At. coordinates are given. The framework from octahedra, statistically occupied by Mg and Ti atoms, contains one-dimensional 3-tube channels along the c-axis, in which occur the mobile Na ions. One of the tubes is occupied totally, the other two partially, with splitting of position, guaranteeing dispersal of Na+. Passage between positions is tighter, than in related structures, consequently the ionic cond. of the ceramic is lower: 2 × 10-3 S/m at 300°.
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    67. 67
      Ishiguro, T.; Tanaka, K.; Marumo, F.; Ismail, M. G. M. U.; Hirano, S.; Somiya, S. Freudenbergite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1978, 34, 255– 256,  DOI: 10.1107/S0567740878002708
      There is no corresponding record for this reference.
    68. 68
      Pospelov, A. A.; Nalbandyan, V. B. Preparation, crystal structures and rapid hydration of P2- and P3-type sodium chromium antimony oxides. J. Solid State Chem. 2011, 184, 1043– 1047,  DOI: 10.1016/j.jssc.2011.03.011
      68
      Preparation, crystal structures and rapid hydration of P2- and P3-type sodium chromium antimony oxides
      Pospelov, A. A.; Nalbandyan, V. B.
      Journal of Solid State Chemistry (2011), 184 (5), 1043-1047CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
      Two new Nax[Cr(1+x)/2Sb(1-x)/2]O2 compds. were prepd. by solid-state reactions in Ar. Their structures were detd. by the x-ray Rietveld method. Both new phases together with NaCrO2-based solid soln. comprise brucite-like layers of edge-shared (Cr,Sb)O6 octahedra, but differ by packing mode of the layers and coordination of the interlayer Na+ ions. A P3 phase exists at x ≈ 0.5-0.58. It is rhombohedral (R3‾m), a 2.966, c 16.937 Å at x ≈ 0.58, with 29% Na+ occupancy of trigonal prisms. A P2 phase exists at x ≈ 0.6-0.7. It is hexagonal (P63/mmc), a 2.960, c 11.190 Å at x ≈ 0.7, with 37% and 33% Na+ occupancy of two nonequiv. trigonal prisms. Both P2 and P3 phases rapidly absorb moisture in air; packing mode is preserved, the a parameter changes slightly, but c increases by 24-25%. Very high Na ion cond. is predicted for both P2 and P3 anhyd. phases.
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    69. 69
      Politaev, V. V.; Nalbandyan, V. B. Subsolidus phase relations, crystal chemistry and cation-transport properties of sodium iron antimony oxides. Solid State Sci. 2009, 11, 144– 150,  DOI: 10.1016/j.solidstatesciences.2008.04.014
      69
      Subsolidus phase relations, crystal chemistry and cation-transport properties of sodium iron antimony oxides
      Politaev, V. V.; Nalbandyan, V. B.
      Solid State Sciences (2009), 11 (1), 144-150CODEN: SSSCFJ; ISSN:1293-2558. (Elsevier Masson SAS)
      Subsolidus phase relations in Na2O-Fe2O3-Sb2Ox system (excluding Na-rich and Sb-rich corners) were studied using powder X-ray diffraction. Samples were prepd. by conventional solid-state reactions at 980-1030 °C followed by quenching. Sb substitution for Fe stabilizes the low-temp. rhombohedral α form of NaFeO2 and enhances ionic cond.: σ(300 °C) = 0.5 S/m, E a = 0.38(3) eV, t e < 0.01 for Na0.8Fe0.9Sb0.1O2 ceramics. Besides known orthorhombic Na2Fe3SbO8, three new compds. have been identified: trigonal Na4FeSbO6, a superlattice of α-NaFeO2 type, a = 5.4217(7) Å, c = 16.2715(1) Å, possible space group P3112; orthorhombic Na2FeSbO5, possibly related to brownmillerite, Pbcn, a = 10.8965(13) Å, b = 15.7178(13) Å, c = 5.3253(4) Å, and one more phase with empirical formula Na4Fe3SbO9, whose pattern could not be indexed. Ion-exchange reactions lead to a delafossite-type superlattice Ag3(NaFeSb)O6 (a = 5.4503(12) Å, c = 18.7747(20) Å, possible space group P3112).
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    70. 70
      Arillo, M. A.; Lopez, M. L.; Perez-Cappe, E.; Pico, C.; Viega, M. L. Crystal structure and electrical properties of LiFeTiO4 spinel. Solid State Ionics 1998, 107, 307– 312,  DOI: 10.1016/S0167-2738(97)00537-7
      70
      Crystal structure and electrical properties of LiFeTiO4 spinel
      Arillo, M. A.; Lopez, M. L.; Perez-Cappe, E.; Pico, C.; Veiga, M. L.
      Solid State Ionics (1998), 107 (3,4), 307-312CODEN: SSIOD3; ISSN:0167-2738. (Elsevier Science B.V.)
      The complex oxide LiFeTiO4 was prepd. by an usual solid state method and its crystal structure was refined by Rietveld's anal. of powder x-ray diffraction data. These results indicate a spinel-type structure in which all Ti cations are in octahedral sites whereas Li and Fe cations are distributed on tetrahedral and octahedral sites, nearly in the same ratio, that could be expressed by the formula: (Li0.47Fe0.53)[Li0.53 Fe0.47Ti]O4. The ionic cond. measured on polycryst. samples was obtained by a.c. techniques at 473-873 K.
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    71. 71
      Kang, K.; Meng, Y. S.; Bréger, J.; Grey, C. P.; Ceder, G. Electrodes with high power and high capacity for rechargeable lithium batteries. Science 2006, 311, 977– 980,  DOI: 10.1126/science.1122152
      71
      Electrodes with High Power and High Capacity for Rechargeable Lithium Batteries
      Kang, Kisuk; Meng, Ying Shirley; Breger, Julien; Grey, Clare P.; Ceder, Gerbrand
      Science (Washington, DC, United States) (2006), 311 (5763), 977-980CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      New applications such as hybrid elec. vehicles and power backup require rechargeable batteries that combine high energy d. with high charge and discharge rate capability. Using ab initio computational modeling, strategies to design high-rate battery electrodes were identified. Tests were performed with [Li(Ni0.5Mn0.5)O2], a safe, inexpensive material that probably has poor intrinsic rate capability. Modification of its crystal structure provided unexpected high-rate capability, better than that of LiCoO2, the battery electrode material of choice.
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    72. 72
      Sai Gautam, G.; Canepa, P.; Urban, A.; Bo, S.-H.; Ceder, G. Influence of inversion on Mg mobility and electrochemistry in spinels. Chem. Mater. 2017, 29, 7918– 7930,  DOI: 10.1021/acs.chemmater.7b02820
      72
      Influence of Inversion on Mg Mobility and Electrochemistry in Spinels
      Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Urban, Alexander; Bo, Shou-Hang; Ceder, Gerbrand
      Chemistry of Materials (2017), 29 (18), 7918-7930CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Magnesium oxide and sulfide spinels have recently attracted interest as cathode and electrolyte materials for energy-dense Mg batteries, but their obsd. electrochem. performance depends strongly on synthesis conditions. Using first-principles calcns. and percolation theory, we explore the extent to which spinel inversion influences Mg2+ ionic mobility in MgMn2O4 as a prototypical cathode, and MgIn2S4 as a potential solid electrolyte. We find that spinel inversion and the resulting changes of the local cation ordering give rise to both increased and decreased Mg2+ migration barriers, along specific migration pathways, in the oxide as well as the sulfide. To quantify the impact of spinel inversion on macroscopic Mg2+ transport, we det. the percolation thresholds in both MgMn2O4 and MgIn2S4. Furthermore, we analyze the impact of inversion on the electrochem. properties of the MgMn2O4 cathode via changes in the phase behavior, av. Mg insertion voltages and extractable capacities, at varying degrees of inversion. Our results confirm that inversion is a major performance limiting factor of Mg spinels and that synthesis techniques or compns. that stabilize the well-ordered spinel structure are crucial for the success of Mg spinels in multivalent batteries.
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    73. 73
      Bayliss, R. D.; Key, B.; Sai Gautam, G.; Canepa, P.; Kwon, B. J.; Lapidus, S. H.; Dogan, F.; Adil, A. A.; Lipton, A. S.; Baker, P. J.; Ceder, G.; Vaughey, J. T.; Cabana, J. Probing Mg migration in spinel oxides. Chem. Mater. 2020, 32, 663– 670,  DOI: 10.1021/acs.chemmater.9b02450
      73
      Probing Mg Migration in Spinel Oxides
      Bayliss, Ryan D.; Key, Baris; Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Kwon, Bob Jin; Lapidus, Saul H.; Dogan, Fulya; Adil, Abdullah A.; Lipton, Andrew S.; Baker, Peter J.; Ceder, Gerbrand; Vaughey, John T.; Cabana, Jordi
      Chemistry of Materials (2020), 32 (2), 663-670CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Mg batteries utilizing oxide cathodes can theor. surpass the energy d. of current Li-ion technologies. The absence of functional devices so far has been ascribed to impeded Mg2+ migration within oxides, which severely handicaps intercalation reactions at the cathode. Broadly, knowledge of divalent cation migration in solid frameworks is surprisingly deficient. Here, we present a combined exptl. and theor. study of Mg migration within three spinel oxides, which reveal crit. features that influence it. Exptl. activation energies for a Mg2+ hop to an adjacent vacancy, as low as ∼0.6 eV, are reported. These barriers are low enough to support functional electrodes based on the intercalation of Mg2+. Subsequent electrochem. expts. demonstrate that significant demagnesiation is indeed possible, but the challenges instead lie with the chem. stability of the oxidized states. Our findings enhance the understanding of cation transport in solid structures and renew the prospects of finding materials capable of high d. of energy storage.
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    74. 74
      Kwon, B. J.; Yin, L.; Park, H.; Parajuli, R.; Kumar, K.; Kim, S.; Yang, M.; Murphy, M.; Zapol, P.; Liao, C.; Fister, T. T.; Klie, R. F.; Cabana, J.; Vaughey, J. T.; Lapidus, S. H.; Key, B. High voltage Mg-ion battery cathode via a solid solution Cr-Mn spinel oxide. Chem. Mater. 2020, 32, 6577– 6587,  DOI: 10.1021/acs.chemmater.0c01988
      74
      High Voltage Mg-Ion Battery Cathode via a Solid Solution Cr-Mn Spinel Oxide
      Kwon, Bob Jin; Yin, Liang; Park, Haesun; Parajuli, Prakash; Kumar, Khagesh; Kim, Sanghyeon; Yang, Mengxi; Murphy, Megan; Zapol, Peter; Liao, Chen; Fister, Timothy T.; Klie, Robert F.; Cabana, Jordi; Vaughey, John T.; Lapidus, Saul H.; Key, Baris
      Chemistry of Materials (2020), 32 (15), 6577-6587CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Lattice Mg2+ in a tailored solid soln. spinel, MgCrMnO4, is electrochem. utilized at high Mn-redox potentials in a nonaq. electrolyte. Complementary evidence from exptl. and theor. analyses supports bulk Mg2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg2+ and O2- exists. Mg/Mn antisite inversion in the spinel is lowered to ~ 10% via postannealing at 350 °C to further improve Mg2+ mobility. Spinel lattice is preserved upon removal of Mg2+ without any phase transformations, denoting structural stability at the charged state at a high potential ~ 3.0 V (vs Mg/Mg2+). Clear remagnesiation upon first discharge, harvesting up to ~ 180 Wh/kg at 60 °C is shown. In the remagnesiated state, insertion of Mg2+ into interstitial sites in the spinel is detected, possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.
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    75. 75
      Robertson, A. D.; Tukamoto, H.; Irvine, J. T. S. Li1+xFe1–3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) based spinels: possible negative electrode materials for future Li-ion batteries. J. Electrochem. Soc. 1999, 146, 3958– 3962,  DOI: 10.1149/1.1392576
      75
      Li1+xFe1-3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) based spinels: possible negative electrode materials for future Li-ion batteries
      Robertson, A. D.; Tukamoto, H.; Irvine, J. T. S.
      Journal of the Electrochemical Society (1999), 146 (11), 3958-3962CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      Members of the spinel solid soln. between LiFeTiO4 and Li4Ti5O12, i.e., Li1+xFe1-3xTi1+2xO4 (0.0 ≤ x ≤ 0.33) have been investigated as possible neg. electrodes for future lithium-ion batteries. Electrochem. behavior and assocd. structural changes have been investigated over the potential range 0.01-2.6 V vs. Li+/Li. Results are promising with anodic capacities in excess of 200 mAh/g or ∼700 mAh/cm3 being obtained over 25 cycles for x = 0.33. Samples contg. Fe have reduced reversible capacity, however, the capacity below 1.00 VLi is greatly increased. A spinel-type structure is retained upon lithiation for all compns. studied, however, the degree of cation disorder increases with Fe content.
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    76. 76
      Miura, A.; Bartel, C. J.; Goto, Y.; Mizuguchi, Y.; Moriyoshi, C.; Kuroiwa, Y.; Wang, Y.; Yaguchi, T.; Shirai, M.; Nagao, M.; Rosero-Navarro, N. C.; Tadanaga, K.; Ceder, G.; Sun, W. Observing and modeling the sequential pairwise reactions that drive solid-state ceramic synthesis. Adv. Mater. 2021, 33, 2100312,  DOI: 10.1002/adma.202100312
      76
      Observing and Modeling the Sequential Pairwise Reactions that Drive Solid-State Ceramic Synthesis
      Miura, Akira; Bartel, Christopher J.; Goto, Yosuke; Mizuguchi, Yoshikazu; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Wang, Yongming; Yaguchi, Toshie; Shirai, Manabu; Nagao, Masanori; Rosero-Navarro, Nataly Carolina; Tadanaga, Kiyoharu; Ceder, Gerbrand; Sun, Wenhao
      Advanced Materials (Weinheim, Germany) (2021), 33 (24), 2100312CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Solid-state synthesis from powder precursors is the primary processing route to advanced multicomponent ceramic materials. Designing reaction conditions and precursors for ceramic synthesis can be a laborious, trial-and-error process, as heterogeneous mixts. of precursors often evolve through a complicated series of reaction intermediates. Here, ab initio thermodn. is used to model which pair of precursors has the most reactive interface, enabling the understanding and anticipation of which non-equil. intermediates form in the early stages of a solid-state reaction. In situ X-ray diffraction and in situ electron microscopy are then used to observe how these initial intermediates influence phase evolution in the synthesis of the classic high-temp. superconductor YBa2Cu3O6+x (YBCO). The model developed herein rationalizes how the replacement of the traditional BaCO3 precursor with BaO2 redirects phase evolution through a low-temp. eutectic melt, facilitating the formation of YBCO in 30 min instead of 12+ h. Precursor selection plays an important role in tuning the thermodn. of interfacial reactions and emerges as an important design parameter in planning kinetically favorable synthesis pathways to complex ceramic materials.
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    77. 77
      Sun, W.; Dacek, S. T.; Ong, S. P.; Hautier, G.; Jain, A.; Richards, W. D.; Gamst, A. C.; Persson, K. A.; Ceder, G. The thermodynamic scale of inorganic crystalline metastability. Sci. Adv. 2016, 2, e1600225,  DOI: 10.1126/sciadv.1600225
      77
      The thermodynamic scale of inorganiccrystalline metastability
      Sun, Wenhao; Dacek, Stephen T.; Ong, Shyue Ping; Hautier, Geoffroy; Jain, Anubhav; Richards, William D.; Gamst, Anthony C.; Persson, Kristin A.; Ceder, Gerbrand
      Science Advances (2016), 2 (11), e1600225/1-e1600225/8CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)
      The space of metastable materials offers promising new design opportunities for next-generation technologicalmaterials such as complex oxides, semiconductors, pharmaceuticals, steels, and beyond. Although metastable phases are ubiquitous in both nature and technol., only a heuristic understanding of their underlying thermodn. exists. We report a large-scale data-mining study of the Materials Project, a high-through put database of d. functional theory calcd. energetics of Inorg. Crystal Structure Database structures,to explicitly quantify the thermodn. scale of metastability for 29,902 obsd. inorg. cryst. phases.We reveal the influence of chem. and compn. on the accessible thermodn. range of cryst. metastability for polymorphic and phase-sepg. compds., yielding new phys. insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compds. can necessarily besynthesized, and propose a principle of 'remnant metastability'-that observable metastable cryst. phases aregenerally remnants of thermodn. conditions where they were once the lowest free-energy phase.
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    78. 78
      Colbow, K.M.; Dahn, J.R.; Haering, R.R. Structure and electrochemistry of the spinel oxides LiTi2O4 and Li4/3Ti5/3O4. J. Power Sources 1989, 26, 397– 402,  DOI: 10.1016/0378-7753(89)80152-1
      78
      Structure and electrochemistry of the spinel oxides LiTi2O4 and Li4/3Ti5/3O4
      Colbow, K. M.; Dahn, J. R.; Haering, R. R.
      Journal of Power Sources (1989), 26 (3-4), 397-402CODEN: JPSODZ; ISSN:0378-7753.
      Li/LiTi2O4 and Li/Li4/3Ti5/3O4 batteries cycle reversibly with little capacity loss for >100 cycles, but have subtle differences in their voltage profiles. As the Li/LiTi2O4 cells have open-circuit voltage ∼2.0 V, the high voltage capacity at ∼2.8 V corresponds to removing Li from the spinel host. By contrast, Li/Li4/3Ti5/3O4 batteries do not show any capacity at high voltage that would correspond to a similar removal of Li from the Li4/3Ti5/3O4 host material. The differences in the battery behavior are interpreted based on the band structure of Li1+xTi2-xO4.
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    79. 79
      Ohzuku, T.; Tatsumi, K.; Matoba, N.; Sawai, K. Electrochemistry and structural chemistry of Li[CrTi]O4 (Fd3̅m) in nonaqueous lithium cells. J. Electrochem. Soc. 2000, 147, 3592– 3597,  DOI: 10.1149/1.1393944
      79
      Electrochemistry and structural chemistry of Li[CrTi]O4 (Fd3m) in nonaqueous lithium cells
      Ohzuku, Tsutomu; Tatsumi, Koji; Matoba, Naoki; Sawai, Keijiro
      Journal of the Electrochemical Society (2000), 147 (10), 3592-3597CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      Li[CrTi]O4 (Fd3m; a = 8.32 Å) having a spinel-framework structure was prepd. and examd. in nonaq. lithium cells. Li/Li[CrTi]O4 cells showed the flat operating voltages of 1.50 V and rechargeable capacity of 150 mAh/g. The X-ray diffraction examns. in this region indicated that Li[CrTi]O4 was reduced to Li2[CrTi]O4 in a topotactic manner. Electrochem. oxidn. of Li[CrTi]O4 was also examd. Redox potential of 4.7 V vs. Li was obsd. while reversibility was poor due to the destruction of crystallite. Differences and similarities between Li[CrTi]O4 and Li[Li0.33Ti1.67]O4 were discussed with respect to operating voltage, reversibility, and insertion scheme.
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    80. 80
      Capponi, J. J.; Billat, S.; Bordet, P.; Lambert-Andron, B.; Souletie, B. Structure, superconducting properties and stoichiometry of Li1-xTi2O4 spinel single crystals. Phys. C 1991, 185–189, 2721– 2722,  DOI: 10.1016/0921-4534(91)91481-I
      80
      Structure, superconducting properties and stoichiometry of lithium titanate (Li1-xTi2O4) spinel single crystals
      Capponi, J. J.; Billat, S.; Bordet, P.; Lambert-Andron, B.; Souletie, B.
      Physica C: Superconductivity and Its Applications (Amsterdam, Netherlands) (1991), 185-189 (Pt. 4), 2721-2CODEN: PHYCE6; ISSN:0921-4534.
      It was shown that lithium can be extd. from the spinel LiTi2O4, with a large variation of the cubic cell parameter from a 8.41 to a 8.30 Å. The spinel network remains unchanged, but important differences in the x-ray diffraction intensities indicate a probable displacement of some titanium atoms. A dramatic change was obsd. in Tc which reach nearly 14 K for relatively small lithium extns.
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    81. 81
      de Picciotto, L. A.; Thackeray, M. M. Insertion/extraction reactions of lithium with LiV2O4. Mater. Res. Bull. 1985, 20, 1409– 1420,  DOI: 10.1016/0025-5408(85)90158-8
      81
      Insertion/extraction reactions of lithium with lithium vanadium oxide (LiV2O4)
      De Picciotto, L. A.; Thackeray, M. M.
      Materials Research Bulletin (1985), 20 (12), 1409-20CODEN: MRBUAC; ISSN:0025-5408.
      Li was inserted into and extd. from the spinel Li∼1.0V2O4 both electrochem. and chem. Electrochem. and structural data show that in Li1+xV2O4 (0 < x ≤ 0.5) Li+ ions are inserted into the interstitial octahedral sites of the Atet[B2]octX4 spinel structure. At x ≈ 0.5, Li+ ions in the tetrahedral A-sites are displaced into the remaining octahedral sites to yield, at x = 1, a rocksalt phase Li2V2O4; the [B2]X4 framework is unperturbed by the lithiation process. This framework also remains intact when Li+ ions are removed from Li∼1.0V2O4 to a compn. Li0.67V2O4. Further extn. of Li from the structure is accompanied by migration of some V ions from the B-sites to the interstitial octahedral sites of the spinel structure. This process reduces the crystal symmetry from cubic to trigonal symmetry. In Li0.27V2O4 the structure resembles that of Li0.22VO2, obtained by delithiation of layered LiVO2, in which the V cations are distributed in a 2:1 ratio between alternate cubic-close-packed O layers; in the LiV2O4 spinel this ratio is 3:1.
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    82. 82
      Barker, J.; Saidi, M. Y.; Swoyer, J. L. Electrochemical insertion properties of lithium vanadium titanate, LiVTiO4. Solid State Ionics 2004, 167, 413– 418,  DOI: 10.1016/j.ssi.2003.09.009
      82
      Electrochemical insertion properties of lithium vanadium titanate, LiVTiO4
      Barker, J.; Saidi, M. Y.; Swoyer, J. L.
      Solid State Ionics (2004), 167 (3-4), 413-418CODEN: SSIOD3; ISSN:0167-2738. (Elsevier Science B.V.)
      The electrochem. insertion properties of the novel spinel phase, lithium vanadium titanate, LiVTiO4 (Fd‾3m, a = 8.236 Å) have been evaluated in nonaq. lithium cells. LiVTiO4 is a member of the general series, LiMTiO4 where M represents a 3d transition metal and was synthesized by a simple solid-state ceramic approach involving lithium carbonate, V2O3 and TiO2. The lithium insertion behavior in the LiVTiO4 relies on the reversibility of the V3+/V4+ redox couple and preliminary electrochem. evaluation indicates a reversible sp. capacity of ∼90 mA-h/g, which represents the cycling of just over half the available lithium in the structure. High-resoln. measurements reveal a structureless and sloping voltage profile consistent with the lithium insertion reactions proceeding via a single-phase mechanism. The lithium extn. and insertion reactions are located at 3.16 and 2.85 V vs. Li, resp., while the sym. nature of the differential capacity data confirms the electrochem. reversibility. By comparison, the structurally related LiCrTiO4 phase demonstrates redox activity in the potential range 4.5-4.8 V vs. Li, although this behavior is accompanied by significant irreversibility. Const. current cycling of representative Li/LiVTiO4 cells indicates moderate insertion stability characterized by ∼15% capacity fade over the initial 20 cycles.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsorginorgau.1c00019.

    • Table of attempted syntheses and products, Rietveld refinements, additional 23Na NMR spectra, and table of Na–O bond distances for selected compounds (PDF)

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    CCDC 2103718, 2103825–2103831, 2103833–2103835, 2103925, 2103928–2103929, 2103933, 2103935, and 2103938 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.


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