Investigation on composition-dependent properties of Mg5xAl23-5xO27+5xN5-5x (0 <= x <= 1): Part I. optical properties via first-principles calculations

摘要

Transparent MgAlON ceramics have attracted attention in recent years as research objects due to their excellent mechanical and optical properties. It is expected that by varying their composition, their properties could be adjusted in a wide range. In this work, six Mg5xAl23-5xO27+5xN5-5x (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) systems were chosen for investigating the composition-dependent optical properties by first-principles calculations. The calculated results for the supercells with the lowest energy suggested that the Mg atoms at 8a sites prefer to coordinate with O atoms only. The calculated optical properties showed that with increasing x, the UV absorption shows a blue shift, the refractive index is decreased, and the Mid-IR absorption is weakened. The compositional dependence of the optical properties is mainly caused by the variation of the covalent character of the bonds in tetrahedra. This investigation provides guidance for the preparation of materials with desirable optical properties.