Dielectric spectroscopy of the antiferroelectric PbHfO3

Dielectric studies of a PbHfO3 (lead hafnate) single crystal undergoing two structural phase transformations at about 163 degrees C (436 K) and 209 de grees C (482 K) were performed in broad frequency and temperature range. Sp ecial attention was paid to the paraelectric phase. Investigations of the c omplex dielectric permittivity in the frequency range 10 Hz to 10 MHz revea led two relaxations of polydispersive and nearly monodispersive (Debye-like ) character connected with space charge behaviour. In the frequency range o f 10(6)-10(9)Hz a polar relaxation mode has been found and related to a dis order in the ph sublattice, Temperature dependence of the dielectric step o f this relaxation corresponds to a sharp anomaly of the epsilon(T) function at the phase transition from the paraelectric to antiferroelectric state. Analysis of temperature evolution of the first order Raman light scattering spectra showed existence of a soft line at this transformation. Crossover of the displacive and order-disorder type of the transformation mechanism i s thus postulated.