Defect Calculations For Yttrium Aluminum Perovskite and garnet Crystals

摘要

Native and impurity point defects in both Yttrium Aluminum Perovskite and Garnet crystals are studied in the framework of the pair-potnetial and the shell model approximations. The calculated formation energies for native defects suggest that the antisite disorder is preferred over the Frenkel and Schottky-like disorder in both YAP and YAG. In non-stoichiometric compounds, the calculated reaction energies indicate that excess of Y_2O_3 or Al_2O_3 is, most likely, to be accommodated by the formation of antisites rather than vacancies or interstitials in the lattice. Enthalpies of the reactions for impurity (Ca~2+, Mg~2+, Sr~2+, Ba~2+, Cr~3+, Fe~3+, Nd~3+, Si~4+) incorporation into both YAP and YAG lattices are presented and discussed. A consistent interpretation of the relevant experimental data is proposed, and some properties of the compounds are predicted.