Structure and magnetic properties of nanocrystalline cobalt ferrite powders synthesized using organic acid precursor method

Nanocrystalline octahedra of cobalt ferrite CoFe2O4 powders were synthesized using the organic acid precursor route. The effect of the calcination temperature, Fe3+/Co2+ molar ratio, calcination time and type of organic acid (oxalic, benzoic and tartaric acids) on the formation, crystallite size, microstructure and magnetic properties was studied systematically. The Fe3+/Co2+ molar ratio was varied from 2 to 1.739 while the annealing temperature was controlled from 400 to 1000 °C for various periods from 0.5 to 2 h. The resulting powders were investigated using X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). XRD results indicate that a well crystallized, single spinel cobalt ferrite phase was formed for the precursors annealed at 600-800 °C for 2 h, using oxalic and tartaric acids as precursors for Fe3+/Co2+ molar ratio 1.818. The crystallite size of as-formed powders was in the range of 38.0-92.6 nm at different operating conditions. The calcination temperature and Fe3+/Co2+ molar ratio have a significant effect on the microstructure of the produced cobalt ferrite. The microstructure of the produced powders was found to be octahedra-shaped. The crystalline, pure cobalt ferrite powders with magnetic properties having a maximum saturation magnetization (76.1 emu/g) was achieved for the single phase at Fe3+/Co2+ molar ratio 1.818 and annealing temperature of 600 °C for 2 h using tartaric acid precursor. © 2010 Elsevier B.V.