Water incorporation into the (Ba1−xLax)2In2O5+x□1−x (0 ≤ x < 0.6) system

(Ba1−xLax)2In2O4+2x(OH)y (0 ≤ x < 0.6; y ≤ 2(1 − x)) compounds were prepared by reacting (Ba1−xLax)2In2O5 + x□1−x (0 ≤ x < 0.6) phases with water vapor. This reaction is reversible. A thermal analysis of the hydration process shows that the stability of hydrated phases decreases when x increases. The filling of oxygen vacancies is complete up to x = 0.2 and decreases for larger x values to reach 17% only for x = 0.5. For x ≤ 0.3 the incorporation of water is not a single-phase reaction. In wet air at 350 °C, a proton contribution to the total conductivity is observed for all compositions but its proportion decreases when x increases.