Dielectric behavior and ac electrical conductivity of Zn-substituted Ni-Mg ferrites

The effect of temperature, frequency and composition on the dielectric behavior and ac electrical conductivity were studied for a series of Zn-substituted Ni-Mg ferrite samples prepared using the usual ceramic technique. The experimental results indicated that the real dielectric constant epsilon', dielectric loss tan delta and real ac electrical conductivity sigma(ac)' increase with increasing temperature. The activation energy E(f) for electric conduction in the ferrimagnetic region, epsilon' and tan delta decrease while the ac conductivity sigma(2)(omega) increases as the frequency increases. epsilon' has high values and tan delta shows dielectric relaxation processes (or peaks) at relatively higher temperatures. The relaxation frequency f(D) shifts to higher values as the temperature increases. sigma(ac)' tan delta and epsilon' increase while the Curie temperature T-C, the activation energy for electric conduction E(f), E(p) (in the paramagnetic region) and E(D) for the dielectric relaxation decrease as Zn ion substitution increases. The parameters n and B for the electrical conductivity sigma(2)(omega) were found to be temperature and composition dependent. Both n and B increase as Zn ion addition increases. B increases while n decreases as the temperature increases; n is zero above the Curie temperature. Empirical formulae are suggested for the temperature and composition dependencies of both parameters n and B.