Effect of sintering temperature on phase structure, microstructure, and electrical properties of (K_0.5Na_0.5)NbO ₃-(Ba_0.6Sr_0.4)_0.7Bi _0.2TiO₃ lead-free ceramics

Lead-free 0.98(K_0.5Na_0.5)NbO₃-0.02(Ba _0.6Sr_0.4)_0.7Bi_0.2TiO₃ (abbreviated as 0.98KNN-0.02BSBT) ceramics were prepared by the conventional solid-state sintering method. Effect of sintering temperature on 0.98KNN-0.02BSBT ceramics was systematically investigated. The frequency dependent dielectric permittivities show that the ceramics sintered at different temperatures are indeed "relaxor-like" ferroelectric ceramics, which possess a diffuse phase transition without a strong frequency dispersion of dielectric permittivity. The diffuseness parameter γ, the comparison of the relaxor behavior based on empirical parameters (ΔT _diffuse) and the slimmer P-E hysteresis loops confirm that the "relaxor-like" characteristics of the ceramics are strengthened with increasing sintering temperature. At the optimum sintering temperature, the dielectric permittivity maximum (E∈ _max) has a value of approximately 2795 (at 1 KHz), tan δ is lower than 2.5 % and the diffuseness parameter γ = 1.68 at a broad usage temperature range (150-350 C), which indicate its potential application in high temperature multilayer ceramics capacitor field.