Potassium sodium niobate ceramics with broad phase transition range: Temperature-insensitive strain

Excellent piezoelectric properties have been achieved in (K,Na)NbO3 (KNN)-based ceramics in the past few years. However, temperature-sensitive strain restricts the use of these ceramics in practical applications. In this work, we report improved piezoelectricity and temperature-insensitive strain in KNN-based ceramics. A broad temperature range for phase boundaries is formed by composition optimization, accounting for the observation of a highly improved strain stability. Interestingly, the strain for a ceramic with x = 0.025 varies by less than 5% and 9%, even if the temperature reaches 150 degrees C and 170 degrees C, respectively, which is comparable to that found for textured-LF4T ceramics. Furthermore, the stability of the original domain configuration with increasing temperature is tested to understand the underlying mechanism for the temperature-insensitive strain. The huge number of original domains retaining a piezoresponse at high temperature due to the extended phase boundary contributes to the temperature-insensitive strain. The present results open a new window for KNN-based ceramics to be used in applications demanding temperature-insensitive piezoelectric properties.