Electronic structure of ZrTiO 4 and HfTiO 4: Self-consistent cluster calculations and X-ray spectroscopy studies

Abstract

Total and partial densities of states of the constituent atoms of ZrTiO 4 and HfTiO 4 titanates have been calculated using a self-consistent cluster method as incorporated in the FEFF8 code. The calculations reveal the similarity of the electronic structure of both titanates and indicate that the valence band of the compounds under consideration is dominated by contributions of O 2p states. These states contribute throughout the whole valence-band region; however their maximum contributions occur in the upper portion of the band. Other significant contributors in the valence-band region are Ti 3d and Zr 4d states in ZrTiO 4 and Ti 3d and Hf 5d states in HfTiO 4. All the above d-like states contribute throughout the whole valence-band region of the titanates; however maximum contributions of the Ti 3d states occur in the upper portion, whilst those of the Zr 4d (Hf 5d) states are in the central portions of the valence band. The FEFF8 calculations render that the bottom of the conduction band of ZrTiO 4 and HfTiO 4 is dominated by contributions of Ti 3d ⁎ states, with also smaller contributions of Zr 4d ⁎/Hf 5d ⁎ and O 2p ⁎ states. To verify the above FEFF8 data, the X-ray emission bands, representing the energy distributions of mainly O 2p, Ti 3d and Zr 4d states, were measured and compared on a common energy scale. These experimental data are found to be in agreement with the theoretical FEFF8 results for the electronic structure of ZrTiO 4 and HfTiO 4 titanates. Additionally, X-ray photoelectron valence-band and core-level spectra were recorded for the constituent atoms of the titanates under study.