Oxygen concentration-related impedance spectroscopic studies of La₂Mo₂O₉ oxide ion conductors

The frequency dispersion of impedance, relaxation, and modulus formalism under oxygen, air, and nitrogen atmospheres are performed on La₂Mo_2−xW_xO₉ (x = 0, 0.3, 0.5, 0.7) phases from 800 °C to room temperature. Thermal analyses on a dilatometer demonstrate the stabilization of the high-temperature cubic phase when the W content is increased. The whole frequency-dependent relaxations from the bulk effect including different oxide ion diffusion to an interfacial contribution are discussed. The oxygen concentration variation (Po₂) has a noticeable influence on the interfacial relaxation of La₂Mo₂O₉ (LMO). A more resistive LMO in the low frequency range with nitrogen treatment is observed differing from the previous conclusions. Besides, an ion dynamic study has been performed and the two sets of overlapping Z″ and M″ peaks in the intermediate temperature range indicate an additional oxide ion jump path in W-doped LMO ceramics.