Reducibility study of oxide-ion conductors La2−xBaxMo2−yAyO9−δ (A = W, Al, Ga) assessed by impedance spectroscopy

The reducibility of oxide-ion conductors La2−xBaxMo2−yWyO9−δ (x = 0, 0.06; y = 0, 0.1, 0.5, 1.0) and La2Mo1.9A0.1O9−δ (A = Al, Ga) were studied in the reducing atmosphere of 5%H2 + Ar by means of impedance spectroscopy measurement. The introduction of Ba at La site in La2Mo2−yWyO9 can lower the sintering temperature by about 100 K in comparison with the La2Mo2−yWyO9 samples. All substitutions can enhance the conductivity and improve the reducibility in the temperature range from 548 to 923 K. The double substitution of Ba and W as well as substitution of Al or Ga at Mo sites has a better stabilizing effect than the single tungsten substitution. Among these substitutions the introduction of Al has the best stabilizing effect.