Electric conduction in Ni-Zn ferrites

The AC electrical conductivity was studied as function of temperature, frequency and composition for a series of Ni1-xZnxFe2O4 ferrite samples prepared by usual ceramic technique. The experimental results indicated that the AC electrical conductivity sigma(2)(omega, T) increases while the activation energy for electric conduction in ferrimagnetic region E-f decreases on increasing the frequency. The real AC (sigma(AC)') and DC (sigma(DC)) electrical conductivities increase as the temperature increases indicating that the studied samples are semiconductors. Both sigma(AC)' and sigma(DC) increase whereas the Curie temperature T-c, activation energies for electric conduction E-f and E-p (in paramagnetic region) decrease as Zn ion substitution increases. The activation energy for electric conduction E-p in the paramagnetic region is higher than that in ferrimagnetic region E-f. The parameter B and exponent it for electrical conductivity sigma(2)(omega, T) in the power law sigma(2)(omega, T) = B omega " were found, respectively, to be composition and temperature dependent. Both n and B increase as Zn ion substitution increases, n decreases whereas B increases as the temperature increases. Empirical formulae were suggested for the temperature dependence of both n and B; compositional dependence of electrical conductivity sigma, and compositional dependence of n and B. (C) 1998 Elsevier Science B.V. All rights reserved.