Abstract:

By using the first-principles calculation, we studied the mechanisms of point defects in Y₄Al₂O₉ (YAM), a promising ternary oxide with excellent optical and thermal properties. It is found that the predominant native defect species is closely dependent on the chemical potentials of each constituent. In the case of O-rich condition, the oxygen interstitial has the very low defect formation energy, followed by the anti-site defects and Al vacancy; in the case of Al-rich condition, the oxygen vacancy yields the lowest defect formation energy, followed by the anti-site defects and Al interstitial. The present result shows that in all the possible chemical potential ranges, anti-site defects have relatively low defect formation energy and might exist in high concentration in YAM. Furthermore, Al_Y anti-site has relatively lower defect formation energy than the Y_Al anti-site throughout. The behaviors of defect complexes under non-stoichiometric condition, such as the Al₂O₃ or Y₂O₃ excess, are also investigated. The results provide helpful guide to optimize the experimental synthesizing of YAM.

Key words: Ternary YeAleO oxide, Defect formation energy, Chemical potential