Temperature and frequency dependent dielectric properties of Ni-Mg-Zn-Co ferrites

The ferrites having general formula Ni0.5Mgx-0.01Zn0.5-yCoy+0.01Fe2O4 (x=0.1, 0.2, 0.3, 0.4 and y=0.1, 0.2, 0.3, 0.4) were prepared by ceramic method. The X-ray diffraction studies of compositions reveal formation of single-phase cubic spinal structure. Dielectric properties such as dielectric constant e', dielectric loss tangent (tan delta), and ac resistivity were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The plots of dielectric constant e' vs frequency show a normal dielectric behavior of spinel ferrites. The variation of loss tangent (tan delta) as a function of frequency shows a decreasing trend for all the samples except for the composition with x=0.3 and y=0.1, and y=0.2. The variation of ac resistivity with frequency of all the samples shows a decreasing trend with increase in frequency, a normal behavior of ferrites. All the variations are explained on the basis of Fe2+/Fe3+ ion concentration on octahedral sites as well as the electronic hopping between Fe2+ Fe3+ ions. (C) 2013 Elsevier B.V. All rights reserved.