Tetragonal–cubic phase transition in BaTiO 3 probed by resonant X-ray emission spectroscopy

Abstract

Ti Kβ resonant X-ray emission spectra (RXES) of barium titanate powder were measured at several temperatures to investigate the microscopic origin of the tetragonal–cubic phase transition. The fluorescence peaks that evolved from de-excitation processes between discrete energy levels are insensitive to temperature change. However, one of two Raman peaks caused by charge transfer (CT) excitation shows an energy shift across the Curie temperature ( T C), accompanied by structural phase transition, which was confirmed by X-ray diffraction measurements. The shifted CT peak retained its intensity at T C because of a fluctuating local polarization. We propose that RXES measurement is a useful method to probe the local covalency in close proximity to an absorbing atom.