Temperature and polarization dependent XANES measurements on single crystal PbTiO₃

We have measured the X-ray Absorption Near Edge Structure (XANES) of single crystal PbTiO₃ as a function of temperature and polarization throughout 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 with the displacement of the Ti atom from a site of centrosymmetry along the c-axis. We find that the dependence upon temperature and polarization of the area under this peak is consistent with the presence of an order-disorder component in the dynamics of this system as it approaches its phase boundary and that the disordering can be ascertained from the XANES with greater accuracy than from the EXAFS alone.