Diffused and successive phase transitions of (K,Na)NbO3-based ceramics with high strain and temperature insensitivity

Phase boundaries realize enhanced piezoelectricity in lead-free (K, Na)NbO₃-based ceramics but suffer from the weakness of undesirable temperature sensitivity. Here, an effective method is designed to develop temperature-insensitive piezoelectricity (small signal piezo-coefficient d₃₃] and large signal piezo-coefficient ]) in KNN-based piezoceramics by constructing the diffused and successive phase transitions, which results in a broadness of the optimal temperature range of the electrical properties. The room-temperature value in KNN-based ceramics modified with BaZrO₃ and (Bi_0.5Na_0.5)HfO₃ reaches as high as 540 (±10) pm V^?1, which is higher than PZT-5H and most reported KNN-based systems. Notably, superior temperature insensitivity of the and P_r values is also observed among the diffused and successive phase transitions region (20-100°C), with <5% fluctuation. In addition, the in situ temperature-dependent d₃₃ measurement shows a high-temperature reliability and less fluctuation (<15%) in a wide temperature range (20-120°C). These results open a new window for further development of highly temperature-insensitive lead-free piezoceramics.