Thermophysical Properties of PbFe_0.5Ta_0.5O₃ Ferroelectric Ceramics with Nanopolar Structure

The thermophysical properties of the PbFe_0.5Ta_0.5O₃ relaxor ferroelectric have been studied in the temperature range 150–800 K. We have revealed anomalies in its heat capacity, thermal diffusivity, and thermal conductivity in the region of the broad ferroelectric transition at T_C ≈ 275 K, the Burns temperature T_B ≈ 690 K, and an intermediate temperature T* ≈ 380 K. The anomalous behavior of heat capacity in the temperature range 200–700 K has been shown to be due to three-level states (Schottky anomaly). We have examined prevailing phonon mechanisms of heat transport in the multiferroic with a nanopolar structure. The anomalous behavior of its thermophysical properties in the temperature range T_B > T > T_C has been attributed to the growth and changes in the system of reorientable nanopolar regions. We have demonstrated that studies of thermophysical properties allow one to determine all characteristic temperatures of relaxor ferroelectrics, related to the formation of a nanopolar structure and its variation with temperature. The results of this study are discussed in combination with structure data.