High temperature stable dielectric properties and enhanced energy-storage performance of (1− x)(0.85Na_0.5Bi_0.5TiO₃ − 0.15Ba_0.8Ca_0.2Ti_0.8Zr_0.2O₃)− xK_0.5Na_0.5NbO₃ lead-free ceramics

Novel high temperature ceramic capacitors (1− x)(Na_0.5Bi_0.5TiO₃ − 0.15Ba_0.8Ca_0.2Ti_0.8Zr_0.2O₃)− xK_0.5Na_0.5NbO₃ were synthesized in the solid-state reaction route. The influence of K_0.5Na_0.5NbO₃ modification on dielectric behavior, energy-storage properties, ac impedance and temperature stable dielectric performance were systematically investigated. The reduced grain size and enhanced relaxor properties are obtained with the addition of KNN. The content of x = 0.1 exhibits a stable permittivity (~ 1630) and dielectric loss (< 0.05) over a relatively broad temperature range (66–230 °C). A variation in permittivity within ± 15% can be observed over a pretty wide temperature range of 66–450 °C. Beyond that, this ceramic shows enhanced energy-storage properties with the density (W_rec) of 0.52 J/cm³ and efficiency (η) of 80.3% at 110 kV/cm. The possible contributions of the grain and the grain boundary to the ceramic capacitance are discussed by the ac impedance spectroscopy.