Dependence of dielectric parameters and AC conductivity on frequency in polycrystalline NiWO4.

The dielectric behaviour of polycrystalline nickel tungstate (NiWO4) sample synthesized by chemical precipitation method is investigated. The dependence of complex permittivity (ε*) and dissipation factor (tanδ) on the frequency are analysed. In order to understand the relaxation process in the sample complex impedance spectroscopy along with electric modulus are studied. This study confirms a single relaxation process in NiWO4 which is a non-Debyetype and the contribution of grain towards the conduction. For the clear understanding of the relaxation behaviour and conductivity of the NiWO4 sample, a simulation of complex impedance data is performed with an equivalent electric circuit. The variation of ac conductivity (σac) with frequency at room temperature is also analysed. It is found that conductivity follows Jonscher's power law. [ABSTRACT FROM AUTHOR]