Dielectric nonlinearity and electric breakdown behaviors of Ba0.95Ca0.05Zr0.3Ti0.7O3 ceramics for energy storage utilizations

Abstract

Ba0.95Ca0.05Zr0.3Ti0.7O3 ceramics were prepared by a citrate method. The dielectric properties of the specimens were examined as a function of temperature, frequency and electric field. Moreover, the energy storage properties and electric breakdown behaviors of the specimens were inspected. Fitting of the dielectric constants under bias electric field to a multipolarization mechanism model resolved the contributions of involved polarization mechanisms. The result indicated that the intrinsic lattice polarization dominated the dielectric constants under strong electric field while the extrinsic contribution of polar nano-regions (PNRs) was basically faded. At the maximum applicable electric field of 160 kV/cm, the specimens achieved an energy storage density of 0.59 J/cm3 and an energy storage efficiency of 72.8%. It was detected that the electric breakdown of the specimens initially occurred on the surfaces immediately adjacent to electrodes, followed by development of an electronic conduction pathway in the bulks. Complex impedance spectroscopy analysis determined that oxygen vacancies were the mobile charge carriers in the specimens. The occurrence of the initial breakdown was explained with respect to accumulation of oxygen vacancies in the specimens induced by strong electric field.