Mechanism of Intrinsic Point Defects and Oxygen Diffusion in Yttrium Aluminum Garnet: First-Principles Investigation

摘要

Formation of intrinsic point defect in yttrium aluminum garnet (YAG) is comprehensively investigated using first-principles calculations. We showed that the defect formation energies of intrinsic point defects closely depend on the possible values of chemical potentials of Y, Al, and O. Both Y_(Al16(a)) anti-site defect, oxygen vacancy V_o, and interstitial O_i might be the preferred defect species when chemical potentials of Y, Al, and O vary in different areas. The O-related defects are also important intrinsic point defects in YAG and deserve to be further examined. The oxygen self-diffusion are investigated and we found that energy barrier of oxygen diffusion is enhanced and decreased by neighboring Y_(Al16(a)) and A1_y anti-site defects, respectively. The results are used to explain the mechanism of experimental observations that Al_2O_3 excess speeds up oxygen diffusion and that Y_2O_3 excess suppresses oxygen diffusion in YAG.