Electrical Characterization of Nanostructured Ferrite Ceramics by Using AC Impedance Spectroscopy

Abstract

In this paper, we report the electrical properties of nanostructured ferrite ceramics by using AC impedance spectroscopy as a function of frequency (100 Hz–10 MHz) in the temperature range from 25 to 100 °C. The nanocrystalline NiFe₂O₄ and ZnFe₂O₄ ferrites were successfully prepared by a conventional sintering of nanosized powders, synthesized by a soft mechanochemical route. X-ray diffraction measurements and scanning electron microscope study confirmed the formation of single cubic spinel structure and nano-dimensional nature of the prepared samples. The temperature-dependent plots between real and imaginary parts of complex impedance reveal the presence of two relaxation regimes which are attributed to grain and grain boundary responses. Complex impedance analysis by means of an equivalent circuit model has been used to separate the grain and grain boundary resistance of these ferrite materials. The temperature dependence of both grain boundary and grain conductivity well follow the Arrhenius law with estimated activation energy of 0.481 and 0.401 eV for NiFe₂O₄, and 0.412 and 0.387 eV for ZnFe₂O₄, respectively. Moreover, the analysis of experimental impedance data indicates the negative temperature coefficient of resistance (NTCR) behavior of both samples usually shown by semiconductors. The conduction mechanism may be due to the hopping of charge carriers present in these ferrite materials.