Nonscalability and nontransferability in the electronic properties of the Y-Al-O system

Abstract

Based on ab initio calculations of electronic structure and properties of five crystals: $\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3,$ ${\mathrm{Y}}_3{\mathrm{Al}}_5{\mathrm{O}}_{12},$ ${\mathrm{YAlO}}_3,$ ${\mathrm{Y}}_4{\mathrm{Al}}_2{\mathrm{O}}_9,$ ${\mathrm{Y}}_2{\mathrm{O}}_3,$ with different Al to Y ratios and local coordinations, it is concluded that the electronic properties of the Y-Al-O system cannot be simply scaled according to cation ratio, and any of the fundamental properties cannot be transferred from one crystal to another. This finding has an implication on the segregation of Y at the internal boundaries in alumina and the precipitate phases contained therein. It is speculated that possible Y-Al interaction may explain the “Y effect” in the Y-containing aluminum oxide. The electronic structure and bonding of ${\mathrm{Y}}_3{\mathrm{Al}}_5{\mathrm{O}}_{12},$ ${\mathrm{YAlO}}_3,$ and ${\mathrm{Y}}_4{\mathrm{Al}}_2{\mathrm{O}}_9$ crystals are discussed in considerable detail in relation to their complex structures.