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

Abstract

The Ti K edge X-ray absorption has been measured under high pressure at room temperature for ATiO₃ 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.

Keywords:

• Ferroelectric instability
• Titanate perovskites
• Ti K-XANES
• High pressure

Acknowledgements

We acknowledge the support of the European Commission under the 6th Framework Program through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract No. RII3-CT-2004-506008