Understanding the 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 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 0.48 Na 0.52 )(Nb 0.955 Sb 0.045 )O 3 -0.01SrZrO 3 - x (Bi 0.5 Ag 0.5 )ZrO 3 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. Unveiling the physical mechanisms of high performance in potassium sodium niobate-based ceramics from diffused multi-phase coexistence and a single domain feature.