Transport properties and thermal expansion of perovskite-like La0.3Sr0.7Fe(Al,Cr)O3−δ ceramics

The use of perovskite-like (Sr,La)FeO3−δ as ceramic membrane materials requires extensive doping in order to increase stability and to suppress thermal and chemical induced expansion. The substitution of iron with aluminum and chromium in La0.3Sr0.7Fe1−x−yAlxCryO3−δ (x = 0–0.4; y = 0–0.2) was found to decrease total conductivity, oxygen permeability and thermal expansion coefficients. The oxygen ion transference numbers of La0.3Sr0.7Fe(Al,Cr)O3−δ, determined by faradaic efficiency measurements in air, vary in the range 10−4 to 10−2 at 1073–1223 K, increasing with temperature. The incorporation of chromium into perovskite lattice enhances the low-p(O2) stability down to oxygen partial pressures of 2 × 10−15 to 2 × 10−14 Pa at 1173–1223 K. The solid solution formation is, however, limited to the values of x ≈ 0.30–0.35 and y ≈ 0.07–0.08.