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 BiFeO₃–BaTiO₃ (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 (d₃₃) shows a considerable increase in ferroelectric phase. In particular, a sharp drop of d₃₃ 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, d₃₃ 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.

高温下从铁电相到弛豫相的相变在压电陶瓷的热去极化过程中起着至关重要的作用。但是，到目前为止，关于这种效应的报道很少，因为热诱导的去极化主要基于异位测量。在这项工作中，已测量了BiFeO ₃ -BaTiO ₃（BF-BT）陶瓷的温度相关介电，压电和铁电响应，以证明实时去极化行为以及它们与铁电弛豫转变之间的关系。可以确认，与温度相关的原位压电系数（d ₃₃）显示出铁电相的大幅增加。特别是d ₃₃急剧下降具有明显的去极化过程与200°C时的铁电-弛豫转变直接相关。讨论了从长距离铁电有序到弛豫转变的发展，这有助于失去优选的畴取向，这是去极化行为的起因，这与常规的异位测量不同。另外，由于居里温度T _c附近的介电常数的急剧提高，d ₃₃表现出第二次小幅增加。实时压电响应的两个增加和两个减少可能为通过调节相变温度来优化高温压电性能提供新的见解。