Effect of heat-treatment on LiZn ferrite hollow microspheres prepared by self-reactive quenching technology

Lithium-zinc ferrite hollow microspheres (LiZn FHMs) containing special surface crystals were synthesized by self-reactive quenching technology. The samples were heat-treated at 1200 A degrees C and held for 4 h. The influence of the heat-treatment on LiZn FHMs was studied. The results show that the surface of hollow microspheres is smooth without heat-treatment. The phase components are Fe2O3, Fe3O4, Li0.435Zn0.195Fe2.37O4, and Li0.5Fe2.5O4. The minimum reflectivity is -13.5 dB, and the corresponding frequency is 7.5 GHz. The effective absorption band lower than -10 dB is 6.2-8.5 GHz, and the bandwidth is 2.3 GHz. After heat-treatment, crystals on the surface of hollow microspheres grow significantly. Multiple-shape micro-nano crystals containing triangular, polygonal, and irregular crystal are generated. However, the phase composition does not change. The real part of the permittivity (epsilon'), the imaginary part of permittivity (epsilon aEuro(3)), the real part of permeability (mu'), and the imaginary part of permeability (mu aEuro(3)) all increase, and the microwave absorption properties at low frequency are significantly increased, with the absorption peak moving to a lower frequency range. The minimum reflectivity is -26.5 dB, and the corresponding frequency changes to 3.4 GHz. The effective absorption band is 2.6-4 GHz, and the bandwidth is 1.4 GHz.