Understanding Piezoelectricity of High-Performance Potassium Sodium Niobate Ceramics from Diffused Multi-phase Coexistence and Domain Feature

The understanding of high piezoelectricity in potassium sodium niobate (KNN)-based ceramics with new phase boundary was still limited within the unpoled sample. Here, the phase structure, domain structure, and phenomenological theory were studied on both unpoled and poled ceramics by taking (0.99-x)(K0.48Na0.52)(Nb0.955Sb0.045)O3-0.01SrZrO3-x(Bi0.5Ag0.5)ZrO3 ceramics as an example. Shifting phase transition temperatures to room temperature can form the coexistence of ferroelectric matrix containing orthorhombic-tetragonal (O-T) coexisted phase and rhombohedral (R)-related polar nanoregions (PNRs), and then the miniatured and nanoscale domain structure can be demonstrated. During the poling process, the R phase-related PNRs can facilitate the domain switching and polarization rotation, resulting in the single domain structure and the enhanced evidence of 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 systematical view to explain the physical mechanisms of enhanced piezoelectricity in KNN-based ceramics.