Ba1-xLaxFe12O19 (x=0.0, 0.2, 0.4, 0.6) hollow microspheres: material parameters, magnetic and microwave absorbing properties

Ba1-xLaxFe12O19 (x = 0.0, 0.2, 0.4, 0.6) hollow ceramic microspheres (HCMs) have been prepared by combining self-reactive quenching method with heat treatment. Their material parameters, magnetic and microwave absorbing properties were investigated. It was observed that after doping of lanthanum, the material parameters showed a little change except hexagonal crystal disappearing. And the magnetic properties of HCMs were decided by lanthanum content and material parameters. With the lathanum increases from 0.0 to 0.6, the saturation magnetization (Ms) values initially increased, and then decreased sharply to a minimum value, and increased again, moreover, the coercive force (Hc) values were reduced first, and then increased, and decrease to a minimum value. Absorbing properties tests indicate that after La3+-doped, at 2 mm thickness, the effective absorbing band (<-10 dB) was reduced to 4.7, 5 and 4.4 GHz, respectively, the minimum reflectance would decrease in low substituted level (x aecurrency sign 0.4) and increase in high level (x = 0.6), and the frequency shifts to low frequency with the increasing of doping content. In 1.5-3 mm range, with the increasing of thickness, the absorption peak of Ba1-xLaxFe12O19 (x = 0.2, 0.4, 0.6) HCMs shifts to low frequency and the absorption intensity increases, the effective absorbing band can up to 10, 8.1 and 8 GHz, respectively.