Activation behavior and dielectric relaxation of nanocrystalline zinc ferrite

•A deviation from universal dielectric response suggests the formation of Schottky diode.•The magnitude of the temperature exponent ‘n’ strongly depends on frequency.•The thermal activation energy for ac conduction decreases with increasing frequencies.•A transformation from broad band limit to narrow band limit has been observed.•The built in voltage and space charge density are calculated from C–V characteristics.

We report the ac conductivity and dielectric relaxation studies of nanocrystalline zinc ferrite prepared by the ball milling. The real part of the complex ac conductivity is found to follow the universal dielectric response σ′(f) ∝ Tnfs and values of both s and n show an anomalous behavior. Both the magnitude of the temperature exponent ‘n’ and thermal activation energy for ac conduction strongly depends on frequencies. The dielectric constant exhibits strong temperature dependence at higher temperature and lower frequencies. The dielectric properties of the samples have been analyzed in terms of electric modulus vector. The complex impedance has also been modeled by an ideal equivalent circuit consisting of grain and grain boundary resistances and capacitances. Considering the formation of Schottky diode at the metallic electrode and semiconductor junction, the diode parameters like built in voltage and space charge density have been extracted from the capacitance-voltage characteristics.

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