Theoretical Studies of the Effect of Ti, Zr and Hf Substitutions on the Electronic Properties of Alpha-Alumina

Abstract

We have investigated the electronic properties of pure Alpha-Alumina (sapphire phase) and the aluminates α-Al2-xTxO3 where T is a transition metal and stands for Ti, Zr and Hf with x = 0.5. In this study we have employed the full potential linear augmented plane wave (FPLAPW) with Generalized Gradient Approximations (GGA) based on the Density Functional Theory (DFT) as implemented in WIEN2K code. The result shows that the electronic band structure and density of state data for pure α-Al2O3 shows that it is a nearly direct band gap insulator with E = 6.04 eV at the Γ point that is comparable with its experimental band gap. We have also shown that the aluminates transition metal substitutions introduced shallow electron states at the bottom of the conduction band edge of pure alpha-alumina which are primarily d-state in character and are originated from the transition metal impurities. The band gap of alumina is decreased for Ti and it is increased for Zr and Hf impurities. Key words: Augmented plane wave, band gap, transition metal, density functional theory.