On the thermodynamic stability of La2Mo2O9−δ oxide-ion conductor

At 608 °C under Ar-H2 flowing atmosphere, La2Mo2O9 phase was found to be unstable and reduction leads to an amorphous phase with composition close to La2Mo2O6.88. The stability of this amorphous phase under Ar-H2 was analyzed by TCXRD and found to be stable below 900 °C. Isothermal TG under controlled pO2 at 1000 °C indicated that La2Mo2O9−δ is not stable below 10−7 Pa and decomposition took place without the formation of La7Mo7O30 or amorphization.