Large Piezoelectric Strain with Superior Thermal Stability and Excellent Fatigue Resistance of Lead-Free Potassium Sodium Niobate-Based Grain Orientation-Controlled Ceramics.

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⟩-oriented texture) (K,Na)NbO-based ceramics with a large piezoelectric response ( d*) = 505 pm V and a high Curie temperature ( T) of 247 °C have been developed. Such a high d* 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 d* value decreasing within only by 6% at a field of 20 kV cm up to 10 cycles. These exceptional properties can be attributed to the vertical morphotropic phase boundary and the highly ⟨001⟩-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.