X-ray absorption spectroscopy on titanate perovskites at the TiK edge

The Ti K edge X-ray absorption has been measured under high pressure at room temperature for ATiO(3) perovskites (A = 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 (PbTiO3) and eventually vanishes at high pressure (BaTiO3). The antiferrodistorsive instability remains unchanged under pressure for CaTiO3 and appears above 5 GPa for SrTiO3. Moreover, it is shown that at room pressure SrTiO3 was locally ferroelectric. A new phase appears for SrTiO3 above 14 GPa with a strong deformation of the oxygen octahedron.