Low frequency anomalous dielectric and elastic behaviour of calcium substituted lead titanate ceramics in the paraelectric phase.

Low frequency complex dielectric and elastic properties of Pb1-xCaxTiO3, x > 0.24, ferroelectric ceramics have been studied as a function of the temperature. Impedance spectroscpy (0.1Hz-10kHz) and Three Point Bending (0.3Hz- 30Hz) methods for dielectric and Young's modulus measurements, respectively, were used. By Raman spectroscopy, the thermal evolution of different vibration modes of some of the compositions was obtained. Both, dielectric and elastic results can be attributed to the some kind of viscous motion of the frontiers between different chemical composition micro regions that remain well above the phase transition temperature. The influence of the region frontiers on those properties seems to be similar to that of the ferroelectric domain walls below the phase transition temperature.