Synthesis of gamma ferric oxide by direct thermal decomposition of ferrous carbonate

Ferrous carbonate was precipitated from the reaction of ferrous sulfate and sodium carbonate in an aqueous medium. The precipitate was calcined at different eating rates (2, 5 and 10 degreesC/min, respectively) up to 500 degreesC and the iron oxides produced were found to be magnetic. X-ray diffraction studies indicated the presence of gamma ferric oxide as a major phase in all the cases. It was found that wet precipitates, faster heating rate and short residence time in the furnace produced gamma ferric oxides with better magnetic properties (coercivity of around 360 Oe and saturation magnetization of 64 emu/g). The effect of aging time of ferrous carbonate precipitates on the magnetic properties was also studied. (C) 2002 Elsevier Science B.V. All rights reserved.