Magnetic and electrical conductivity studies of zinc doped cobalt ferrite nanofluids

Abstract

To synthesize stable nanofluids of zinc-doped cobalt ferrite (ZnxCo(1-x)Fe2O4) with various dopant concentrations (x = 0, 0.1, 0.2, 0.3 and 0.4), a two-step method is adopted. X-ray diffraction pattern was used to confirm the phase purity of the ferrite whereas EDAX analysis was performed to determine the chemical composition. The magnetic studies performed on the samples reveal that they show monodomain structure and superparamagnetic nature. The electrical conductivity of the undoped and zinc doped cobalt ferrite nanoparticles is studied and is explained through hopping mechanism. The electrical conductivity of all the nanofluids is higher than that of water, the base fluid, due to the formation of electrical double layer (EDL) in the dispersion. An increase of 90% in electrical conductivity is reported in the Zn0.2Co0.8Fe2O4 sample at room temperature compared to base fluid, which is due to higher surface charge and zeta potential. The effect of temperature on electrical conductivity of nanofluids is elucidated using percolation effect of ferrite nanoparticles in the base fluid. Also, it is noted that magnetic field has no effect over the formation of EDL, and hence, there is no change in electrical conductivity with respect to applied field. The experimental values are compared with Maxwell and Shen's models, which are found compactible with the framework of Shen's model.