A new perspective on the process of intrinsic point defects in α-Al2O3

Abstract

First-principles plane-wave pseudopotential calculations have been performed to study the charge states and energetics of intrinsic point defects as vacancies, interstitials and antisite atoms in α-Al₂O₃, and thus a new perspective on the process of intrinsic point defects has been proposed. Considering the various charge states for each intrinsic point defects, V_Al³⁻, V⁰_O, Al_i³⁺, O_i²⁻, Al_O³⁺, and O_Al³⁻, not all in their fully ionized states are found to be most stable and in pure Al₂O₃. From the formation energies of individual point defects, the antisite atom O_Al will be readily formed in α-Al₂O₃ in an O-rich environment. By combination of charge states and formation energies, the defect types of Schottky, Al Frenkel and antisite pairs formed are found to be dependent on the O condition, and the most stable Schottky defect type is not the commonly considered {3V_O²⁺:2V_Al³⁻}. There are two types of possible O Frenkel defects under both O conditions, yet the most stable defect is {O_i¹⁺:V_O¹⁻} rather than the commonly believed {O_i²⁺:V_O²⁻}. The bizarre configuration and the charge state of Schottky and Frenkel defects predicated in this work provide a new perspective on the process of intrinsic point defects in α-Al₂O₃.