Dielectric relaxation behavior of AxCo1-xFe2O4 (A = Zn, Mg) mixed ferrites

Samples of A(x)Co(1-x)Fe(2)O(4) (A = Zn, Mg; x = 0.0, 0.5) ferrite were synthesized by chemical co-precipitation method. Room temperature Rietveld - refined X-ray diffraction pattern elucidate the formation of single-phase cubic structure with Fd3m space group for all prepared samples. Slight variation in the lattice parameter of Mg doped CoFe2O4 has been observed when compared with CoFe2O4 and Zn0.5Co0.5Fe2O4. The variation of permittivity and ac conductivity as a function of frequency reveals that dispersion in all these ferrites is attributed to Maxwell-Wagner type of interfacial polarization. The minimum value of loss tangent (similar to 0.04) at 5 kHz makes A(x)Co(1-x)Fe(2)O(4) most suitable material for microwave application. Temperature dependent dielectric constant and loss tangent of all the three samples shows an increasing trend with increase in temperature. The activation energy (E-a) for CoFe2O4, Co0.5Mg0.5Fe2O4 and Co0.5Zn0.5Fe2O4 were found to be 0.81 eV, 0.76 eV and 0.63 eV respectively. The electrical modulus study clearly reveals the presence of non-Debye type of dielectric relaxation in the present material. (C) 2012 Elsevier B. V. All rights reserved.