The influence of electrical field on (K,Na)NbO₃-based ceramics over polymorphic phase transition composition region

By investigating the responding behavior of Li modified (K,Na)NbO₃ ceramics under external electrical field, a coincidence phenomenon had been observed. It was found that the amplitude of piezoelectricity enhancement for these ceramics with pure orthorhombic, coexistence and tetragonal phase were consistent with the variation amplitude for the transition temperature from orthorhombic to tetragonal (T_O-T). The interpretation of the remnant polarization (P_r) had rationally demonstrated the enhancement of piezoelectricity for these three kinds of ceramics. The residual polarization energy induced by remnant polarization (P_r) was about to affect the thermodynamic equilibrium state of these ceramics and accordingly ΔT_O-T varied with these poled ceramics.