Synthesis of magnetite by coprecipitation and sintering and its characterization

Magnetite powder was synthesized via chemical co-precipitation method using FeCl₃?·?6H₂O and FeCl₂?·?4H₂O as salts and ammonium hydroxide (25% NH₄OH) solution as precipitating agent. The phases, composition and morphology of the magnetite was characterized by X-ray diffraction (XRD), micro laser Raman spectroscopy and scanning electron microscopy–energy dispersive X-ray spectroscopy. The XRD and Raman studies confirmed the formation of magnetite phase only. The results showed that the particles were properly crystallized with no other impurity. Very fine and non-uniform powder sizes were observed even after sieving operation. The magnetite particles were also characterized after sintering the powder at 1100°C, grinding and sieving. The resultant powder size in the range of 105–125?µm was obtained. After sintering, magnetite peaks got sharpened due to increase in the crystallite size. Raman peaks even at a higher laser power were observed for magnetite that were absent before sintering. Hematite peaks observed for the un-sintered powder at higher laser power was attributed to oxidation by laser radiation/heat. Efficiency of the co-precipitation process (before sintering) was established to be ～85%.