Enhanced Oxygen Ion Conductivity and Ionic Conduction Mechanistic Visualization in Tetragonal Zircon-Type Pr_1–<i>x</i>Sr<i>_<i>x</i></i>VO_{4–0.5<i>x</i>}

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 Pr_0.975Sr_0.025VO_4-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.