Dielectric relaxation in bismuth layer-structured BaBi4Ti4O15 ferroelectric ceramics

The dielectric properties of BaBi4Ti4O15 ceramics were investigated as a function of frequency (102–106 Hz) at various temperatures (30°C–470 °C), covering the phase transition temperature. Two different conduction mechanisms were obtained by fitting the complex impedance data to Cole–Cole equation. The grain and grain boundary resistivities were found to follow the Arrhenius law associated with activation energies: Eg ∼ 1.12 eV below Tm and Eg ∼ 0.70 eV above Tm for the grain conduction; and Egb ∼ 0.93 eV below Tm and Egb ∼ 0.71 eV above Tm for the grain boundary conduction. Relaxation times extracted using imaginary part of complex impedance Z″(ω) and modulus M″(ω) were also found to follow the Arrhenius law and showed an anomaly around the phase transition temperature. The frequency dependence of conductivity was interpreted in terms of the jump relaxation model and was fitted to the double power law.