X-ray absorption spectroscopy on titanate perovskites at the Ti K edge

摘要

The Ti K edge X-ray absorption has been measured under high pressure at room temperature for ATiO_(3) perovskites (A velence Ca, Sr, Ba and Pb). The pre-edge features have been used to determine the local distortion around the Ti atom as a function of applied features. The ferroelectric local instability decreases when pressure is increased (PbTiO_(3)) and eventually vanishes at high pressure (BaTiO_(3)). The antiferrodistorsive instability remains unchanged under pressure for CaTiO_(3) and appears above 5 GPa for SrTiO_(3). Moreover, it is shown that at room pressure SrTiO_(3) was locally ferroelectric. A new phase appears for SrTiO_(3) above 14 GPa with a strong deformation of the oxygen octahedron.