Non-stoichiometric of CoFe_2O_4 nanoparticles supported on an amorphous silica matrix

摘要

Non-Stoichiometric CoFe_2O_4 nanoparticles dispersed in an silica matrix with a silica content of 87 wt% and Co/Fe molar ratio of 1:1,were prepared by the sol-gel method using an ethanolic solution of tetraethoxysilane and either iron(III) and cobalt(II) nitrates or iron(II) and cobalt(II) acetates. The influence of different metal precursors on the xerogels were examined by X-Ray Diffraction (XRD),Transmission Electron Microscopy( TEM) and N_2 physisorption measurements at 77K. Magnetic properties of the samples were investigated by field cooled FC and zero field cooled ZFC measurements.Depending on the metlaprecursor,different spineloxides of a few nanometers were observed in the samples treated at 350degC.After heating at 900degC non-stoichiometric CoFe-2O_4 was formed in both samples,whose average particle size was only slightlylarger than in samples treated at 350degC.