High-temperature stability study of the oxygen-ion conductor La0.9Sr0.1Ga0.8Mg0.2O3-x

Because of their high oxygen-ion conductivity, LaGaO3-based perovskites substituted on the A and B sites, such as La0.9Sr0.1Ga0.8Mg0.2O3-x (LSGM), are considered to be promising alternatives to replace YSZ currently used in SOFCs. LSGM was prepared by a complexing sol-gel process and characterised by XRD, TG-DTA and conventional weight analysis. The room- temperature structure is orthorhombic, space group Pnma, with a = 0.5534, b = 0.5507, c = 0.7800 nm. After heating at 1000 C, the lattice parameters of LSGM shift a little, and La4SrO7 and SrLaGaO4 separate from the parent phase, which may further affect other properties. The weight change of LSGM at 750 C is insignificant and the phase is also stable after heating at 750 C in H2 for a total of 132 h. Defect chemistry modelling supports the view that LSGM is not single phase at 1000 C. 19 refs.