Study on the effect of pressure on the properties of intrinsic point defects in monoclinic zirconia: Ab initio calculations

First-principles calculations were performed to investigate the effects of external pressure on the properties of intrinsic point defects in monoclinic zirconia. Our results show that when the applied external pressure increases from atmospheric pressure to 14.9 GPa, the formation energies of oxygen vacancies decrease with increasing pressure, while the formation energies of the cation and anion interstitials increase all over the pressure regime investigated. Among them the most remarkable change occurs in neutral zirconium interstitial with an increase of 2.21 eV. In particular, the formation energy of zirconium vacancy depends strongly on its charge state. For all the chemical potential and Fermi level considered, the cation and anion vacancies are the most stable defects in all cases. The present calculations also reveal that the formation energies of Frenkel defects could be raised by external pressures, while the energetics of Schottky defects are not much affected. Moreover, the charge state transition of defects is found to be greatly influenced by the external pressures, and thus the stability diagram of defects in ZrO₂ is strongly dependent on external pressures. Our findings suggest that external pressures should raise the concentration of oxygen vacancies significantly.