Influence of heat treatment conditions on the structure and magnetic properties of barium ferrite BaFe12O19 hollow microspheres of low density

Barium ferrite BaFe12O19 hollow microspheres of low density (about 2.50 g cm−3) were synthesized without BaFe2O4 or other intermediate phase by spray pyrolysis technique, combined with co-precipitation precursor and followed further heat treatment. The relationships between the microstructure, magnetic properties and the sintering temperature, time were investigated. Hollow microspheres, constituted by nanometer particles, showed a broad particle distribution of 2–15 μm. When the sample was sintered at 900 °C for 3 h or at 1100 °C for 2 h, pure BaFe12O19 ferrite was formed. With the increase of the sintering temperature or time, the grain size and preferential growth orientation were influenced, the saturation magnetization (Ms) had a small increase, and the coercive force (Hc) decreased obviously.