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

Sun, Xi-xi, Zhang, Junwei, Lv, Xiang, Zhang, Xi-xiang, Liu, Yao, Li, Fei, Wu, Jiagang
Journal of materials chemistry A 2019 v.7 no.28 pp. 16803-16811
ambient temperature, ceramics, phase transition
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.