In-situ measurement of thermal depolarization in tetragonal BS-PT piezoelectric ceramics

High temperature depolarization poses a significant challenge to the practical application of piezoelectric/ferroelectric materials. Determining the depolarization temperature (T_d) in such materials is crucial for evaluating their performance under high temperature conditions. Here, we propose a method for observing thermal depolarization by examining the 90º domain switching induced strain. Our results show that the differential thermal expansivities of unpoled and poled tetragonal BiScO₃-PbTiO₃ (BS-PT) piezoelectric ceramic samples can distinguish between thermal expansion strain and 90º domain switching induced strain. The effectiveness of our proposed method is further confirmed by quantitatively analyzing the 90º domain via X-ray diffraction. Compared to the in-situ resonance-antiresonance impedance spectrum, our method allows for more accurate testing of depolarization temperature, demonstrating significant potential for the direct observation of thermal depolarization in piezoelectric/ferroelectric materials.