Complex impedance and dielectric properties of an Mg-Zn ferrite

Complex impedances of a sintered polycrystalline Mg0.5Zn0.5Fe2O4 ferrite in the frequency range of 15 mHz to 13 MHz were measured at several temperatures in the range of 273-373 K. The complex-plane impedance spectra indicate that the material can be represented by a two-layer leaky capacitor which corresponds to the bulk and the grain boundary phenomena at high and low frequencies respectively. A series resistance of about the same value at all temperatures is observed. This resistance is believed to be due to the external contacts and the electrodes. Agreement between experimental and simulated data is established by assuming a frequency-dependent capacitive element. The results for the relative dielectric constant epsilon'(r) and dielectric loss epsilon'(r) at low frequencies are discussed as being attributed to the interfacial polarization; at high frequencies a Debye-like relaxation from orientational polarization is dominant. The dependence of impedance and dielectric properties on temperature and frequency are discussed.