Ba7Nb4MoO20: A Proton or Oxide Ion Conductor?

H units, leading to reduced bulk conductivity in the pristine and slightly Nb-rich compositions at <400 °C. However, by heating up over 400 °C, the bulk conductivity in the wet atmosphere surpasses that in the dry one, benefitting from an injection of protons into the perovskite blocks to release free O5 ions for oxide ion conduction, indicating that hydration may provide extra oxide ions to enhance the oxide ion conduction.