Understanding the piezoelectricity of high-performance potassium sodium niobate ceramics from diffused multi-phase coexistence and domain feature

Abstract

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)(K_0.48Na_0.52)(Nb_0.955Sb_0.045)O₃–0.01SrZrO₃–x(Bi_0.5Ag_0.5)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.