Association of structural and enhanced transport properties in RE substituted cobalt nanoferrites

Spinel ferrites belong to an important class of compounds which has variety of electrical and magnetic applications. Neodymium doped cobalt ferrites with composition CoFe2-xNdxO4 where x = 0.00, 0.05, 0.10, 0.15, 0.20 were synthesized by wet chemical route called simplified sol-gel method. Prepared samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) for structural analysis. All the samples were found spinel cubic belonging to Fd-3m space group. To analyze temperature effects on phase transition and to check thermal stability differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were done. Sample with x = 0.00 was found to be thermally more stable than remaining samples. Electrical analysis was done by using two probe method. DC electrical resistivity and drift mobility of sintered samples were measured as a function of temperature in the range from room temperature to 450 °C. It was observed that DC electrical resistivity has a direct dependence on dopant concentration but indirect dependence on temperature. Verwey hopping model was used to describe the results of DC electrical resistivity. Activation energy calculated from linear plots of DC resistivity for all samples was in the range of 0.532-0.594 eV. Rarely reported thermal transport properties that include thermal conductivity, thermal diffusivity and volumetric heat capacity were measured by Advantageous Transient Plane Source (ATPS) method. All the samples showed values near to that of thermal insulators. Thermal conductivity of all samples was increased up to 100-120 °C and then decreased. This behavior was thoroughly studied.