Electrical properties and impedance analysis of Bi0.5Ba0.5FeO3 ceramic

Ba0.5Bi0.5FeO3 ceramic was fabricated by conventional solid-state reaction method. The microstructures and electrical properties were characterized by X-ray diffraction, scanning electron microscopy, direct current (DC) resistance-temperature measurement and alternative current (AC) impedance analysis. According to the analysis, Ba0.5Bi0.5FeO3 ceramic is a cubic perovskite-type compound, and its grain size is about 1.0 μm. In the measured temperature range of 16—280 ℃, Ba0.5Bi0.5FeO3 ceramic shows obvious negative temperature coefficient thermistor characteristic, and the thermistor constant and activation energy of the ceramic are 6490 K and 0.558 eV, respectively. The temperature dependence of dielectric constant reveals that below 280 ℃ no phase transition occurs. The AC impedance characteristic in the ceramic can appropriately be modeled in terms of an equivalent electrical circuit comprising of a series combination of three parallel RQ components in connection with the grain, grain shell and grain boundary effects. The fitting results are in good agreement with the experimental data. The components of grain, grain shell and grain boundary, showing NTC characteristic, have the order of resistive contribution of Rg>Rs>Rgb. In the temperature range 25—115 ℃, the significant mismatch between the peaks of parameters Z″(ω) (imaginary part of impedance) and M″(ω) (imaginary part of electric modulus) suggests a development of persistent localized conduction in Ba0.5Bi0.5FeO3 ceramic.