X-ray-absorption spectroscopy on strontium titanate under high pressure

Abstract

The pressure dependence of the interatomic distances and their mean-square deviations (Debye-Waller factors) in ${\mathrm{SrTiO}}_{3}$ are studied by x-ray-absorption spectroscopy in a diamond anvil cell up to 15 GPa. The pressure dependence of Sr-O and Sr-Ti interatomic distances have been determined and compared with x-ray-diffraction data. The comparison confirms the occurrence of a structural phase transition induced by pressure. In the low-pressure phase the Sr-O and the Sr-Ti bond compressibilities are very close to those deduced from x-ray-diffraction data, and a Debye model can describe the pressure dependence of the oxygen and titanium Debye-Waller factors. On the contrary, in the high-pressure phase, the mean Sr-O and Sr-Ti bond compressibilities become smaller, and the Debye-Waller factors increase with pressure, showing an increase of the oxygen and titanium static disorder due to various Sr-O and Sr-Ti distances.