Crystallization processes and microwave absorption properties of amorphous LiZn ferrite hollow microspheres

In this work, amorphous Lithium-Zinc ferrite hollow microspheres (LiZn FHMs) were prepared by using self-reactive quenching technology with NaCl aqueous solution (15 wt%) as the quenching medium. Heat-treatment for 4 h at 300, 600, 900 and 1200 °C was used to obtain LiZn FHMs with different degree of crystallization. The morphology, phases and microwave absorption properties were investigated by SEM, XRD, and vector network analyzer. The results show that polarization increases first and decline then with the increasing of heat-treatment temperatures. So the value of εʺ also increases and then decline. Natural resonance is the magnetic loss mechanism of amorphous LiZn FHMs (room temperature) and those with heat-treatment at 300, 900 and 1200 °C. However, natural resonance and eddy current loss are the magnetic loss mechanism with heat-treatment at 600 °C. The microwave absorption properties increase first and decline then with the increasing of heat-treat temperature, which is caused by the decline of orientational polarization of electric dipole moment and increasing of space charge polarization.