TEMPERATURE AND POLARIZATION-DEPENDENT XANES MEASUREMENTS ON SINGLE-CRYSTAL PBTIO3

We have measured the X-ray Absorption Near Edge Structure (XANES) of s ingle crystal PbTiO3 as a function of temperature and polarization thr oughout its tetragonal phase. The broken centrosymmetry at the Ti site gives rise to a distinctive peak in the region before the main rising edge. The strong polarization dependence of this peak is consistent w ith the displacement of the Ti atom from a site of centrosymmetry alon g the c-axis. We find that the dependence upon temperature and polariz ation of the area under this peak is consistent with the presence of a n order-disorder component in the dynamics of this system as it approa ches its phase boundary and that the disordering can be ascertained fr om the XANES with greater accuracy than from the EXAFS alone.