The La(1-x)SrxFe(1-y)GayO3-delta perovskites are one of the most promising materials for catalytic membrane reactor because of their excellent oxygen semi-permeation, low thermal expansion coefficient and good chemical stability at high temperature (700-1000 degrees C) under a wide range of oxygen partial pressure (from 0.21 to 10(-19) atm). In this paper, the thermal expansion coefficient (TEC) and the oxygen semi-permeation of La(1-x)SrxFe(1-y)GayO3-delta perovskite in relation with Sr and Ga substitutions have been measured and discussed. The chemical stability of La(1-x)SrxFe(1-y)GayO3-delta perovskite formulations under diluted methane atmosphere is tested and discussed. This study leads to identify the Sr and Ga substitution ratios presenting the best compromise between high oxygen semi-permeation, low thermal expansion coefficient and good chemical stability in working conditions. 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. (C) 2011 Elsevier B.V. All rights reserved.