Antisite defect in nonstoichiometric yttrium aluminum garnet: Experimental and first-principles calculation

Antisite defects in nonstoichiometric yttrium aluminum garnet (YAG) were investigated systematically with experiments and first-principles calculation based on density functional theory. Transparent YAG ceramics with different deviations from stoichiometry have been prepared and the lattice constants increase with the increase of deviation. Calculations show that YAl,16a is the most preferred antisite defect and the concentration of defects increases as the sintering temperature increased. High sintering temperature results in high concentration of YAl defects, however YAl defects may avoid secondary phase in Y2O3-rich YAG. It is found that formation energy of AlY antisite defect is very high, therefore the concentration of AlY antisite defects is very low even at high temperature. For Al2O3-rich YAG, it is impossible to avoid the formation of secondary phase. The deviation from stoichiometry has great influence on the transmittance and optical quality of transparent ceramics.