Temperature and frequency-dependent dielectric properties of Zn substituted Li-Mg ferrites

The DC and AC resistivity (rho(DC), rho(AC)), dielectric constant (epsilon') and dielectric loss tangent (tan delta) of Zn substituted Li-Mg ferrites having the general formula LixMg0.4Zn0.6-2xFe2+xO4 (where x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) have been investigated as a function of composition, temperature and frequency. The compositional variation of DC resistivity and dielectric constant show the inverse trend with each other. The sample with x = 0.15 (Zn = 0.3) shows lowest DC resistivity and highest dielectric constant. The dielectric constant increases slowly with temperature in the beginning and then abruptly at about 473 K and above. The AC resistivity and dielectric constant of all the samples decrease with increase in frequency exhibiting normal ferrimagnetic behaviour. The variation of dielectric loss tangent with frequency showed maxims in the 2-40 kHz frequency range. These maxima are also found to shift towards low-frequency region as the content of Zn increases. All the variations are explained on the basis of Fe2+ and Fe3+ concentrations on octahedral sites and electronic hopping frequency between Fe2+ and Fe3+ ions. (C) 1999 Elsevier Science B.V. All rights reserved.