BaFe12O19 particles with high magnetization were produced using an acetone-aided coprecipitation process. An aqueous solution of iron and barium nitrates, in an Fe3+/Ba2+ molar ratio of 12, was added in a stirred precipitation liquid medium composed of H2O, CH3(CO)CH3 and NH4OH. After reacting metallic ions with ammonia, the precipitates were formed, centrifugally filtered, freezing-dried and calcined. Effects of amount of the acetone in the precipitation liquid medium on the formation of crystalline BaFe12O19 were investigated. The presence of acetone in the precipitation liquid medium can greatly promote formation of the crystalline BaFe12O19 at temperature as low as 650 oC and can enhance magnetization of the derived particles. On the other hand, raising the calcination temperature can effectively accelerate development in crystallite morphology and magnetic characters of the barium hexaferrites. While the barium hexaferrite powder obtained without acetone additions and calcined at 1000 oC had magnetization (measured at 50 kOe; M(50 kOe)) of 63.5 emu/g, remanence magnetization (Mr) of 31.3 emu/g and coercivity (Hc) of 4.7 kOe, the single magnetic domain sizes BaFe12O19 powder with M(50 kOe) of 70.6 emu/g, Mr of 34.4 emu/g and Hc of 3.7 kOe was produced at 1000 oC, using a precipitation liquid medium of 64 Vol.% acetone.
Journal of Magnetism and Magnetic Materials 341, pp.79-85