AC conductivity and electric modulus analysis of manganese-doped barium calcium titanate ceramics

This paper reports the study of charge transport in manganese (Mn) doped barium calcium titanate ceramics using ac conductivity and electric modulus analysis. Various parameters such as σdc, ωH and s have been extracted from the fitting of experimental ac conductivity considering the Almond-West law. With Mn doping, the values of activation energy for dc conduction (Edc) are found in the range 1.041–1.061 eV. The conduction in the studied ceramics occurs via Overlapping large Polaron tunneling model. Thermal activation energy of electrical conduction (Edc) has been found to decrease with Mn concentration. Parameters, viz. β, M″max and fmax, are evaluated by electrical modulus data fitting with KWW function. Values of β confirm non-Debye-type relaxation behavior. The values of relaxation time (τM″) in the range 0.42μs to 1620μs and decreases with temperature, indicating that the relaxation process is thermally activated and occurs faster at higher temperatures and increases with Mn²+ doping. The activation energy for relaxation (ER) are in the range from 1.21 eV to 1.34 eV.