THE FERROELECTRIC PHASE-TRANSITION IN PBTIO3 FROM A LOCAL PERSPECTIVE

XAFS of Pb and Ti in PbTiO3 provides quantitative information on the l ocal structure of this ferroelectric perovskite. It was found that bot h Pb and Ti remain in off center positions above T-c. The local distor tions above T-c are about 50-70% of their values at 15 K. The local di stortions above T-c are correlated over at least several unit cells. T hese results suggest that the off center displacements of the Pb and T i are caused by local interactions and not just by a farce field assoc iated with the order parameter.