Contributions of intrinsic and extrinsic polarization species to energy storage properties of Ba0.95Ca0.05Zr0.2Ti0.8O3 ceramics

Abstract

Ba0.95Ca0.05Zr0.2Ti0.8O3 ceramics were prepared at different sintering temperatures by citrate precursor and solid-state reaction methods, respectively. The crystal structure and microstructure of the specimens were characterized. In view of energy storage capacitor utilizations, the dielectric properties of the specimens were investigated at room temperature as a function of frequency and applied electric field. Moreover, the nature of mobile charge carriers in the specimens was diagnosed by complex impedance spectroscopy at elevated temperatures. While the dielectric constants of the specimens prepared by different methods are quite different (4.4 × 103–2.2 × 104 at 10 kHz) at zero electric field, the energy storage densities at an identical strong electric field are similar (e.g. 0.32–0.41 J/cm3 at 120 kV/cm). The dielectric constants under bias electric field were fitted to a multipolarization mechanism model to resolve the contributions of intrinsic and extrinsic polarization mechanisms. It turned out that the extrinsic contributions fade out within low electric field range (<20 kV/cm) and thereby the intrinsic lattice polarization governs the overall dielectric responses at higher fields. Based on the fitting result, the energy storage properties of the specimens were interpreted.