Microwave absorption properties of LiZn ferrites hollow microspheres doped with La and Mg by self-reactive quenching technology

Lithium-Zinc ferrite hollow microspheres (LiZn FHMs) doped with La and Mg were synthesized by Fe + Zn + Fe2O3 + O-2 + Li2CO3 reactive system based on self-reactive quenching technology. Influence of La and Mg doping on the surface morphology, phase structure and microwave absorption properties of LiZn FHMs were investigated. The results show that the surface morphology of LiZn FHMs changes little and are still composed of unnoticeable multi-shape crystal grains, whether they are doped or not. The phases are mainly made up of Fe3O4, Fe2O3, Li0.435Zn0.195Fe2.37O4 and Li0.5Fe2.5O4 without doping. The phases remain unchangeable after Mg doping, while LaFeO3 appears in the phase components after La doping. When LiZn ferrites are without doping, their minimum reflectivity at 4 mm is -14 dB at 7.5 GHz, and the effective absorption frequency band less than -10 dB is 6.4-8.6 GHz, with the bandwidth of 2.2 GHz. Compared with that without doping, the minimum reflectivity increases after Mg doping, and the effective absorption frequency band less than -10 dB disappears. After La doping, the minimum reflectivity is -30.2 dB at 6.2 GHz, and the effective absorption frequency band is 4.7-7.7 GHz, with the bandwidth of 3 GHz. It is found from the present investigations that the microwave absorption properties are improved after La doping, and those of LiZn FHMs after Mg doping are reduced. (C) 2015 Elsevier B.V. All rights reserved.