Spectrophotometric Determination of the Hole Concentration in the Superconductor YBa2Cu3O7-x. An Undergraduate Experiment

Jack I. Hoppé and Mounir A. Malati
Mid Kent College of Higher and Further Education, Horstead, Chatham, Kent ME5 9UQ, United Kingdom
J. Chem. Educ., 2005, 82 (2), p 299
DOI: 10.1021/ed082p299
Publication Date (Web): February 1, 2005
History, Education, and Documentation

Abstract

The preparation and characterization of the superconductor YBa2Cu3O7-x, or YBCO, are described. The experiment is based on the reduction of the holes by FeCl2 in 1 M HCl solution under laboratory vacuum. This reaction leads to the formation of Fe(III) chloride, mainly in the form of tetrahedral [FeCl4]–, together with Cu(II) chloride, mainly in the form [CuCl4]2–. The electronic spectra of the two species, as well as Fe(II) chloride, are described. An intense absorption band for Fe(III) at 335 nm is well separated from a weaker band for Cu(II), and from an even weaker band for Fe(II). The absorbance at 335 nm of the solution resulting from the addition of HCl to solid YBCO subsequent to the above reaction, together with absorbances of standard FeCl3 in 1 M HCl, were used to calculate the concentration of Fe(III). This is equivalent to the hole concentration in the superconductor. The results are compared with those obtained by the well known iodometric method.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Laboratory Instruction

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Oxidation / Reduction
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  • Received: August 03, 2009

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