Enhanced Oxygen Ion Conductivity and Ionic Conduction Mechanistic Visualization in Tetragonal Zircon-Type Pr1–xSrxVO4–0.5x

Oxide-ion conductors based on tetrahedral anion-related oxides have attracted considerable attention due to their high oxygen-ion conductivity and potential applications in clean energy devices, such as solid-state fuel cells. In this study, we report the improvement of oxide-ion conductivity by Sr2+ doping in isolated tetrahedral zircon-type PrVO4. It is found that Pr0.975Sr0.025VO4-δ features the highest oxide-ion conductivity of 2.62 × 10-3 S·cm-1 at 800 °C under air, with an oxygen transport number of 0.93. The formation and stabilization of oxygen vacancy defects, as well as the oxide-ion migration mechanism in PrVO4, were investigated through combining experimental characterizations and computing simulations. The results indicate that the concentration of oxygen vacancy defects increases with Sr2+ substitution, and the vacancies are accommodated by the formation of corner-sharing V2O7 dimers. Oxygen-ion migration proceeds via a cooperative mechanism involving V2O7-dimer breaking and reforming assisted by synergistic rotation and deformation of neighboring VO4 tetrahedra. The results provide valuable insights for further investigation and optimization of zircon-type oxides as potential oxide-ion conductors for electrochemical devices.