Synthesis and Characterization of Cobalt Ferrite Nanoparticles

Abstract

Coprecipitation method is widely used to synthesize ferrite nanoparticles. Effect of pH, reaction temperature, annealing temperature and zinc substitution on the structural and magnetic properties of the cobalt ferrite and zinc substituted cobalt ferrite nanoparticles is studied in this thesis by x-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The crystallite size ranges from 26.50 to 128.92 nm with increasing pH and from 26.50 to 128.92 nm with increasing reaction temperature. A gradual increase in crystallite size is observed with increasing zinc content although it is much less than the as-synthesized cobalt ferrite nanoparticles. Magnetic properties of the samples are also affected by reaction conditions. Saturation magnetization increases by increasing the reaction temperature as well as the sintering temperature. Coercivity ranges from 16.02 to 1247.32 Oe and remanence from 0.14 to 11.63 emu/g of the series obtained with increasing pH. No particular trend is detected as coercivity ranges from 88.49 to 431.14 emu/g and remanence from 0.73 to 8.99 Oe with the increasing reaction temperature. While both remanence and coercivity shows maximum values when the samples are annealed at 800 ºC. Also an increasing trend of saturation magnetization with increasing annealing temperature is observed. The zinc substituted cobalt ferrite nanoparticles are superparamagnetic in nature and have maximum saturation magnetization of 38.98 emu/g with zinc content of 0.4.