Co2+ substituted Li-Ni ferrites with compositional formula Li0.45-0.5xNi0.1CoxFe2.45-0.5xO4, where 0.02≤x≤0.1 in steps of 0.02 were prepared by the chemical sol-gel method and sintered at 900°C for 4h. X-ray diffraction studies confirmed the formation of single phase with spinel structure in all the samples. The lattice constant and crystallite size evaluated from XRD data were found to increase with increase of Co2+ content and the calculated crystallite size ranges from 35-59nm. The microstructure of the samples was studied by using Scanning Electron Microscopy. The room temperature dielectric constant and dielectric loss were measured as a function of frequency from 100Hz-1MHz and they showed a dispersive behaviour. The variation has been explained by Verwey’s mechanism of electron hopping and Koop’s two layer model. The study of the frequency variation of A.C. conductivity was found to increase with the increase of frequency. The substitution of Co2+ plays significant role in influencing the various structural and electrical properties. The results obtained and mechanisms involved are thus discussed.

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