Preparation and magnetic properties of composite powders of hollow microspheres coated with barium ferrite

The composites of barium ferrite coated on hollow ceramic microspheres are successfully prepared using sol–gel combustion method. The crystal structure and magnetic properties with different weight ratio of hollow microspheres in the composite are studied with X-ray diffraction (XRD), differential scanning calorimetry (DSC)/DTA and vibrating sample magnetometry (VSM). The results show that the composites are composed of barium ferrite and hematite. The reason resulting in the phase transition process is proposed. With the increase of microspheres, the phase content of barium ferrite and specific saturation magnetization of composites decrease. The specific saturation magnetization and coercivity are 16.5 emu/g and 4900 Oe for composite powders having 50 wt.% of microspheres. Besides, its density is only 1.8 g/cm3. The application of composites in magnetic recording and light electromagnetic absorbing fields is promising.