Valence Spectra and Electronic Structure of Perovskites

Abstract

The results of studying the X-ray photoelectron and X-ray OK(alpha) emission valence-level spectra of perovskite-like oxides (SrTiO(3), KNbO(3), PbZrO(3), KTaO(3), Na(0.7)WO(3), BaBiO(3)) are reported. Both types of spectra are compared on the binding energy scale, and the contribution of the O2p states to the valence band of the above compounds is determined. The results are compared to the band structure calculations for KNbO(3) and KTaO(3) and to the available electronic structure calculations for SrTiO(3), NaWO(3), and BaBiO(3). The O2p states appear to have the nonbonding character at the valence band top of the perovskites. The O3d states are not involved in chemical bonding and are not mixed with the d states of the transition-metal atoms in the compounds in question. The changes in binding energy for the inner electrons of d metals are considered to be the manifestation of intercationic interaction in perovskites. The Wf(7/2,) (5/2) line for Na(0.7)WO(3) has a very complicated shape that can be approximated by a superposition of two spectra for tungsten in the oxidation states W(4+) and W(6+) taken in the ratio W(4+) : W(6+) = 0.42 : 0.58.