Investigation of oxygen point defects in cubic ZrO₂ by density functional theory

The energetics of formation and migration of the oxygen vacancy and interstitial in cubic ZrO₂ are investigated by density functional theory calculations. In an O-rich environment, the negatively charged oxygen interstitial is the most dominant defect whereas, the positively charged oxygen vacancy is the most dominant defect under O-poor conditions. Oxygen interstitial migration occurs by the interstitialcy and the direct interstitial mechanisms, with calculated migration energy barriers of 2.94 eV and 2.15 eV, respectively. For the oxygen vacancy, diffusion is preferred along the (100) direction, and the calculated energy barriers are 0.26 eV for V_O²+, 0.27 eV for V_O¹+ and 0.54 eV for V_O⁰. These results indicate that oxygen diffusivity is higher through the vacancy-migration mechanism.