Charge transfer transitions, luminescence properties, and electronic structure of YTaO4 and YNbO4

Abstract

We studied the structural and electronic properties of YTaO4 and YNbO4 by means of accurate first principle total energy calculations. The calculations are based on density functional theory (T.WT). The total energy, electronic band structure, and density of states calculations are performed via the full potential linear-augmented plane wave approach, as implemented in the WIEN2K code, within the framework of DFT. The results show that the valence bands of tantalate and niobate systems are from O 2p states. Conduction bands are divided into two parts. The lower conduction band is mainly composed of Ta 5d or Nb 4d states and the upper conduction band involves a contribution mainly from Y 4d states of YTaO4 or YNbO4. The efficient bandgaps in yttrium tantalate and niobate are determined to be about 4.8 and 4.1 eV respectively. The agreement between the calculations and the experimental data is excellent. The efficient bandgap and a simple model, illustrating excitation and emission process in considered host lattices are discussed.