Influence of sintering temperature on electrical properties of (K_0.4425Na_0.52Li_0.0375)(Nb_0.8825Sb_0.07Ta_0.0475)O₃ ceramics without phase transition induced by sintering temperature

Lead-free (K_0.4425Na_0.52Li_0.0375)(Nb_0.8825Sb_0.07Ta_0.0475)O₃ (KNLNST) piezoelectric ceramics are synthesized by the conventional solid-state reaction method. The sintering temperature and poling temperature dependence of ceramic properties are investigated. Previous studies have shown that variation of sintering temperature can cause phase transition, similar to the morphotropic phase boundary (MPB) behavior induced by composition changes in Pb(Zr,Ti)O₃ (PZT). And the best piezoelectric performance can be obtained near the phase-transition sintering temperature. In this research, phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained. The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density, which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides. Combined with the effect of poling temperature, the peak values of the piezoelectric properties are d₃₃ = 313 pC/N, k_p = 47%, ε_r = 1825, tanδ = 0.024, T_o–t = 88 ℃, and T_C = 274 ℃.