Thermally stable piezoelectric properties of (K, Na)NbO3-based lead-free perovskite with rhombohedral-tetragonal coexisting phase

A feasible replacement for lead-based piezoelectric ceramics is desperately required for increasing environmental concerns. Benefiting from the construction of a rhombohedral-tetragonal (R-T) phase boundary, a potential lead-free candidate (Na0.5K0.5)NbO3-(Bi0.5Li0.5)TiO3-BaZrO3 is presented in this study, with a large piezoelectric coefficient d33 of 330 pC/N and a unipolar strain of 0.16% at 4 kV/mm. More importantly, the piezoresponse is extremely thermally stable that the strain can maintain a considerable value of 0.12% at the temperature as high as 190 °C, rendering the current system very promising for piezoelectric actuator applications. The temperature dependent phase structure evolution as well as piezoelectric response is investigated systematically for interpretation of underlying mechanisms.

A niobate-based lead-free piezoelectric ceramic with outstanding thermal stability is presented by constructing a rhombohedral-tetragonal (R-T) phase boundary. The unipolar strain can maintain 0.12% up to 190 °C. Experimental evidences and phenomenological explanations reveal the importance of phase structure engineering in lead-free piezoelectrics.220