Comparative Study on the Microstructural and Magnetic Properties of Cobalt Ferrites Synthesized by Ceramic and Oxidation Wet Methods

摘要

CoFe$_{2}$O$_{4}$ and CoMn$_{0.2}$Fe$_{1.8}$O$_{4}$ ferrites were synthesized using standard solid state phase ceramic method and coprecipitation and oxidation method. X-ray diffraction, MÖssbauer spectroscopy, and surface electron microscopy were used to characterize the samples'' microstructures. Vibrating sample measurement and strain gauge technique were used to characterize the magnetic and magnetostrictive properties of both powders and sintered samples, respectively. The specific magnetization increased from 55 emu/g for stoichiometric ferrite samples obtained by conventional method to 179 emu/g for coprecipitated ferite powders respectively. In the manganese substituted cobalt ferrite case the specific magnetization increased only twice, from 77 emu/g to 168 emu/g. The maximum magnetostrictive coefficient of coprecipitated samples of 145 ppm is smaller compared to that of solid state phase ceramic samples of 195 ppm. The most important benefit in the case of the coprecipitated and oxidized samples is the four fold increase of the maximum strain derivative compared to solid state phase ceramic samples.