Broad-temperature-span and improved piezoelectric/dielectric properties in potassium sodium niobate-based ceramics through diffusion phase transition

Abstract

Continuous progress of piezoelectric coefficient (d33) and dielectric constant (εr) are obtained in (K, Na)NbO3 (KNN)-based lead-free piezoceramics by phase boundary formation, while usually accompanying by the poor temperature/thermal stability, which are not conductive to actual applications. In this work, the perovskite-type compound Bi(Ni2/3Nb1/3)O3 is designed and added into KNN ceramic. This additive can not only shift orthogonal-tetragonal (O-T) phase transition towards room temperature to enhance d33, but also make the O-T phase transition becoming diffusion in a broad temperature range. Furthermore, the piezoelectricity is further elevated by optimizing polarization via Ce3+ doping. Finally, the enhanced d33 is achieved with the excellent thermal stability from room temperature to> 350 °C. Besides, the high εr of ~ 1150 and low dielectric variation of ≤ ± 15 % can be obtained in a quite broad temperature span from room temperature to ~ 300 °C. These overall performances of this work show the potential multifunctional applications in high-temperature piezoelectric and dielectric devices.