The effect of charged defects on the stability of implanted helium and yttrium in cubic ZrO2: a first-principles study

Abstract

The effect of charged defects on the stability of implanted He and Y atoms has been fully investigated to gain insight into the occupation mechanism of defects in cubic ZrO₂ using first-principles calculations. For the intrinsic point defects in ZrO₂, the configurations of V_O²⁺, I_O²⁻, V_Zr⁴⁻, and I_Zr⁴⁺ are dominant, which have the lowest formation energy over the widest Fermi level range, respectively. He atoms at neutral Zr vacancies have the lowest incorporation energy (0.438 eV), illustrating that the V_Zr⁰ is probably the most stable trapping site for He atoms. For the Y atoms implanted in ZrO₂, the most stable configuration of Y_Zr¹⁻ is obtained over the widest Fermi level range. In the Y-doped ZrO₂, the incorporation energy of He at the site of Oct₂ interstitial is the lowest (1.058 eV). For He atoms trapped at vacancies, He-V_Zr⁰ has the lowest incorporation energy of 0.631 eV. These results indicate that He atoms preferentially occupy the sites of V_Zr⁰. The state of electric charge plays a significant role in the formation of defects in the ionic compound. The present simulation results provide a theoretical foundation for the effect of charged defects on the stability of He atoms, which contributes to the understanding of the microscopic solution behaviour of He atoms in perfect ZrO₂ and Y-doped ZrO₂.