Investigation of dielectric relaxations and conduction mechanism in Aurivillius ceramic Bi₅Ti₃FeO₁₅

Aurivillius Bi₅Ti₃FeO₁₅ (BTFO) ceramic is synthesized by the generic solid-state reaction route. The room temperature X-ray diffraction (XRD) study confirms that the compound is having single-phase without any impurity. Surface morphology of the prepared sample ensures that the presence of microstructural grains with size around 0.2 to 2 µm is observed. Dielectric properties of sample are investigated as a function of frequency of about 100 Hz to 1 MHz at various temperatures (303 K ≤ T ≤ 773 K). The Nyquist plots of impedance data exhibit a semi-circular arc in high temperature region, which is explained by the equivalent electrical circuit (R₁C₁) (R₂QC₂). Our results indicate that resistance as well as capacitance of grain boundary is more prominent over the grains. Analysis of ac conductivity data is done by using Jonscher universal power law (σ_ac=σ_dc+Aωⁿ) which confirms that the conduction process is dominated by the hopping mechanism. The activation energies calculated for relaxation and conduction processes are very close to each other (0.32 eV to 0.53 eV) by which we conclude that the same type of charge carriers are involved in both the processes.