Temperature dependence of electronic structure on the ferroelectric phase transition ofBaTiO3

X-ray Raman scattering spectra of ferroelectric $\mathrm{BaTi}{\mathrm{O}}_{3}$ were measured under excitation around the Ti $K$-absorption edge. Density of states of the unoccupied Ti $3d$ state was measured using Ti $2p$ core excitations. Anisotropy was observed in the ferroelectric phase with respect to spontaneous polarization direction. This anisotropy decreased with rising temperature and vanished in the paraelectric phase. Experimental results showed the ion displacement and electronic structure are closely related, and the hybridization between Ti $3d$ and O $2p$ states affects the ferroelectric phase transition.