Direct observation of electric field-induced tetragonal-orthorhombic phase transition in KNN-based piezoelectric ceramics via in-situ synchrotron diffraction

Abstract

Straightly investigation of the structure-property relationship in the multiphase (K,Na)NbO3-based systems is attractive since constructing multiphase coexistence has been proved as the leading strategy to achieve high piezoelectric performance. In this study, we directly revealed a reversible electric field-induced tetragonal-orthorhombic (T-O) phase transition and the structural correlation to the high performance by in-situ synchrotron X-ray diffraction. The T and O phase coexistence is continuously observed during the whole bipolar electric cycling, among which O phase is energetically preferred in high field region and T phase is near coercive electric field. The synergistic crystal lattice variations and extensive phase fraction changes suggest that the reversible transition between the coexisted T and O phases acts as a bridge for polarization switching. Insights from this work will facilitate a deep understanding of the enhanced properties in KNN-based piezoelectrics and also shed light on the structural-related mechanism of other piezoelectric systems.