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Article

Comparison of Oxygen Permeability and Stability of Perovskite Type La_0.2A_0.8Co_0.2Fe_0.8O_3-_δ (A = Sr, Ba, Ca) Membranes

Shiguang Li, Wanqin Jin, Pei Huang, Nanping Xu,* and Jun Shi

Membrane Science & Technology Research Center, Nanjing University of Chemical Technology, Nanjing 210009, P. R. China

Y. S. Lin

Department of Chemical Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0171

Michael Z.-C. Hu^† and E. Andrew Payzant^‡

Chemical Technology Division, Metals & Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6224

Ind. Eng. Chem. Res., 1999, 38 (8), pp 2963–2972

DOI: 10.1021/ie9900014

Publication Date (Web): July 15, 1999

Corresponding author. Tel: 0086-025-3319580; Fax: 0086-025-3300345; E-mail: npxu@dns.njuct. edu. cn.

†

Chemical Technology Division.

‡

Metals & Ceramics Division.

Abstract

The oxygen permeation and stability of La_0.2A_0.8Co_0.2Fe_0.8O₃_-_δ (A = Sr, Ba, Ca) perovskite-type membranes were studied at high temperatures and low oxygen partial pressures. The oxygen vacancy diffusivity and concentration gradient calculated from the unsteady-state and steady-state oxygen data for the three membranes decrease in the order of Sr > Ba > Ca. The activation energies for oxygen permeation increase in the order of Sr < Ba < Ca. The oxygen permeation data of the three membranes can be explained by the average bond energy, free volume, and critical radius of the materials. After exposure to air at 1173 K for 10 h, part of La_0.2Sr_0.8Co_0.2Fe_0.8O₃_-_δ transforms to La₂O₃, SrO, CoO, and Fe and the crystallite size of the perovskite phase decreases. These changes were not observed for La_0.2Ba_0.8Co_0.2Fe_0.8O₃_-_δ under the same conditions, indicating that La_0.2Ba_0.8Co_0.2Fe_0.8O₃_-_δ membrane is much more stable than La_0.2Sr_0.8Co_0.2Fe_0.8O₃_-_δ at high temperatures and low oxygen partial pressures.