Strain effects of temperature and electric field induced phase instability in (Na,K)(Nb,Sb)O3-LiTaO3 lead-free ceramics

The temperature and electric field induced phase instability were found to produce distinctly different temperature-dependences of small- and high-field strains in the proximity of orthorhombic (O) to tetragonal (T) polymorphic phase transition of (Na,K)(Nb,Sb)O3-LiTaO3 lead-free ceramics. As evidenced by means of in-situ and ex-situ synchrotron x-ray diffraction and quantitative analyses, both O-T phase coexistence and intermediate monoclinic (Mc) phase were believed to promote intrinsic piezoelectric strains. Further increase of high-field strains with temperature was ascribed to enhanced contributions from field-induced reversible Mc-T phase transition, plus little extrinsic contribution from non-180° domain switching which was unexpectedly hindered near the phase boundary.