The inferences of ZnO additions for LKNNT lead-free piezoelectric ceramics

By the conventional solid-state liquid-phase sintering technique, Li_0.058(K_0.480Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ + x wt% ZnO (x = 0, 0.2, 0.4, 0.6, 0.8, 1, 3) lead-free piezoelectric ceramics were fabricated. The addition of ZnO liquid-phase sintering promoters could improve the grain-growth of LKNNT ceramics significantly and its inferences were investigated detailed in this paper. The crystal phases and micro-structures were analyzed by means of the X-ray diffraction and scanning electronic microscopy, respectively. Using the impedance analyzer, the dielectric constant, loss tangent, Curie temperature, phase transition point, and electromechanical coupling factor were measured. And the piezoelectric constants were measured by the d₃₃ meter. Compared to pure LKNNT ceramic (sintered at 1090°C, d₃₃ = 279 pC/N, and k_p = 0.46), for x = 0.6 specimen, even though the optimal d₃₃ and k_p values were only 272 pC/N and k_p = 0.44, but the optimal sintering temperature have been improved from 1090°C to 1020°C successfully.