Polar orientation and extension in a novel crystallographic model for PbTiO₃-based perovskites explaining the experimental ferroelectric thermal anomalies

PbTiO 3 -based ferroelectric solid-solution ceramics have been widely used for electromechanical devices. However, it is still challenging to separate and control the contributions to the electromechanical functionalities, mainly as a function of temperature, where thermal anomalies and phase transitions can be observed. This study investigates the ultrasonic velocity and attenuation and the dielectric, ferroelectric and structural features of Pb 0.55 Ca 0.45 TiO 3 ceramics from low temperatures (10 or 115 K) up to room temperature as an example of A -site isovalent substitution in PbTiO 3 . Such a combination of information makes possible the phenomenological deconvolution of the effects of ferroelectric domain wall pinning and structural features on spontaneous electric polarization. The room-temperature symmetry was determined as Pna 2 1 . The results show that this model refined by the Rietveld method for synchrotron X-ray diffraction patterns from 115 K to room temperature can explain the polarization extension features of these materials during heating. This study shows a correlation between structural thermal anomalies and low-temperature electric polarization in PbTiO 3 -based ferroelectric ceramics.