Environment-friendly lead-free piezoelectric materials with high piezoelectric response and high stability in a wide temperature range are urgently needed for various applications. In this work, grain orientation-controlled (with a 90% ⟨001⟩c-oriented texture) (K,Na)NbO3-based ceramics with a large piezoelectric response ( d33*) = 505 pm V-1 and a high Curie temperature ( TC) of 247 °C have been developed. Such a high d33* value varies by less than 5% from 30 to 180 °C, showing a superior thermal stability. Furthermore, the high piezoelectricity exhibits an excellent fatigue resistance with the d33* value decreasing within only by 6% at a field of 20 kV cm-1 up to 107 cycles. These exceptional properties can be attributed to the vertical morphotropic phase boundary and the highly ⟨001⟩c-oriented textured ceramic microstructure. These results open a pathway to promote lead-free piezoelectric ceramics as a viable alternative to lead-based piezoceramics for various practical applications, such as actuators, transducers, sensors, and acoustic devices, in a wide temperature range.
Keywords: KNN-based ceramics; RTGG; large piezoelectric strain; lead-free piezoelectric ceramics; thermal stability.