The understanding of high piezoelectricity in potassium sodium niobate (KNN)-based ceramics with a new phase boundary has been limited to unpoled samples. Here, the phase structure, domain structure, and phenomenological theory were studied on both unpoled and poled samples by taking (0.99 − x)(K0.48Na0.52)(Nb0.955Sb0.045)O3–0.01SrZrO3–x(Bi0.5Ag0.5)ZrO3 ceramics as an example. Shifting the phase transition temperatures to room temperature can result in the coexistence of a ferroelectric matrix containing an orthorhombic–tetragonal (O–T) coexisting phase and rhombohedral (R)-related polar nanoregions (PNRs), and then the miniature and nanoscale domain structure can be demonstrated. During the poling process, the R phase-related PNRs can facilitate domain switching and polarization rotation, resulting in a single domain structure and enhanced evidence of the R phase. Therefore, high piezoelectricity originates from a single domain feature as well as the diffused multi-phase coexistence in association with R phase related PNRs. This study provides a systematic approach to understand the physical mechanisms of enhanced piezoelectricity in KNN-based ceramics.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors acknowledge financial support from the National Natural Science Foundation of China (NSFC No. 517222008), the Key Technologies Research and Development Program of Sichuan Province (No. 2018JY0007), and the Undergraduate Student's Research and Innovation Fund of Sichuan University (No. 201810610075).