Perovskite-type oxides for high-temperature oxygen separation membranes

Oxygen permeation through dense ceramic membranes of perovskite-like SrCo0. 9-xFe0.1CrxO3-delta (x = 0 01-0 05), Sr1-x-y Ln(x)CoO(3-delta)(Ln =La, Nd, Sm, Gd;x= 0.30-0.35;y = 0-0.10), SrCo1-xTixO3-delta (x= 0.05-0.20) and LaM1 -xNixO3-delta (M = Ga, Co, Fe;x=0-0.6) was studied. The SrCoO3-delta-based solid solutions with cubic perovskite structure were found to exhibit highe st permeation fluxes compared to other membranes. However, high thermal exp ansion coefficients and interaction with gas species such as carbon dioxide may complicate the employment of SrCoO3-delta membranes for oxygen separat ion membranes. Alternatively, the LaGa1-xNixO3-delta (x= 0.2-0.5) perovskit es, having significant permeation fluxes as well as thermal expansion coeff icients in the range of (10.8-11.6) x 10(-6) K-1, were demonstrated to be s uitable as membrane materials at oxygen pressures from 1 x 10(-2) to 2 x 10 (4) Pa. Testing oxygen permeation at oxygen partial pressures of 1-60 arm s howed that only oxides with a high oxygen deficiency such as SrCo0.85Ti0.15 F3-delta possess sufficient oxygen permeation fluxes. The oxygen permeabili ty of perovskites on the basis of LaGaO3 and LaCoO3-delta was found to be n egligible at oxygen pressures above 15 atm, caused by low oxygen vacancy co ncentration and ionic conductivity of such ceramic materials. (C) 1999 Else vier Science B.V. All rights reserved.