LAUSR

Phase transition from a ferroelectric to relaxor phase at high temperature plays a crucial role on thermal depolarization process for piezoceramics. However, so far very few have been reported concerning the effect because the thermally induced depolarization was mainly based on ex-situ measuring. In this work, temperature-dependent dielectric, piezoelectric, and ferroelectric responses of BiFeO 3 –BaTiO 3 (BF–BT) ceramics have been measured to evidence real-time depolarization behavior as well as their relationship with ferroelectric-relaxor transition. It is confirmed that in-situ temperature-dependent piezoelectric coefficient ( d 33 ) shows a considerable increase in ferroelectric phase. In particular, a sharp drop of d 33 with the evidently depolarization process is directly related to the ferroelectric-relaxor transition at 200 °C. The development of the long-range ferroelectric order to the relaxor transition aiding the loss of preferred domain orientation is discussed as the origins for the depolarization behaviors, which is different from usual ex-situ measurements. In addition, d 33 showed a second increase to a small extent due to the drastic improvement dielectric constant near Curie temperature T c . The two increases and two decreases of in-time piezoelectric responses may provide a new insight to optimize the high-temperature piezoelectric performance by regulating phase transition temperature.