Large-scale production of strontium ferrite by molten-salt-assisted coprecipitation

Large-scale production of strontium hexaferrite (SrFe12O19) particles was successfully achieved by molten-salt-assisted coprecipitation. A mixture of sodium hydroxide and sodium carbonate was served as mixed precipitant to obtain ferrite precursors. The effects of the Fe3 +/Sr2 + molar ratio, calcination temperature, calcination time, and molten-salt amount on the formation, morphology and magnetic properties of SrFe12O19 particles were investigated. The resultant particles were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. Single-phase SrFe12O19 particles, with particle sizes of 0.8–1.2 μm, were obtained from the precursor (with a Fe3 +/Sr2 + molar ratio of 10) being calcined at 950 °C for 2 h using the mass ratio (NaCl to precursor) of 0.3. The saturation magnetization, remanent magnetization and coercivity were about 62 emu/g, 37 emu/g, and 4310 Oe, respectively. A comparison of the products obtained at different preparation-scales was also done. The results showed that it was easier to control the particle morphology using molten salt synthesis and more economical on a large-scale production.