Effect of CaZrO3 on phase structure and electrical properties of KNN-based lead-free ceramics

Abstract

(1 − x)[0.93(K_0.5Na_0.5)NbO₃–0.07LiNbO₃]–xCaZrO₃ (KNN–LN–xCZ) lead-free piezoelectric ceramics have been prepared by the conventional solid state reaction method and investigated to differentiate the effects of polymorphic phase transition. The crystal structure of the ceramics changed from orthorhombic to tetragonal at x ≥ 0.04, and then both the orthorhombic and tetragonal phases coexisted in the region of 0.04 < x < 0.08 composition, and the orthorhombic–tetragonal phase transition temperature was modified to around room temperature. Remarkably, piezoelectric and ferroelectric properties have been obtained for KNN–LN–xCZ ternary system with x = 0.04, in which the piezoelectric parameter of d^*₃₃ was 320 pm V⁻¹ with Curie temperature T_c = 350 °C, strain level = 0.16% at 50 kV cm⁻¹ and remnant polarization P_r = 27.2 μC cm⁻².