La(1―x)SrxFe(1―y)GayO3―δ perovskite membrane: Oxygen semi-permeation, thermal expansion coefficient and chemical stability under reducing conditions

La(1-x)SrxFe(1-y)GayO3-delta perovskites are one of the most promising materials for catalytic membrane reactors because of their excellent oxygen semi-permeation, low thermal expansion coefficient and good chemical stability at high temperature (700-1000 C) under a wide range of oxygen partial pressures (from 0.21 to 10 exp(-19) atm). The thermal expansion coefficient and the oxygen semi-permeation of La(1-x)SrxFe(1-y)GayO3-delta perovskites in relation to Sr and Ga substitutions were measured. The chemical stability of La(1-x)SrxFe(1-y)GayO3-delta perovskite formulations under a diluted methane atmosphere was tested. The Sr and Ga substitution ratios giving the best compromise between high oxygen semi-permeation, low thermal expansion coefficient and good chemical stability under working conditions were determined. In this way, one of the best compromises between good oxygen permeation fluxes, dimensional and chemical stabilities are La0.6Sr0.4Fe0.6Ga0.4O3-delta and La0.6Sr0.4Fe0.7Ga0.3O3-delta.