Influence of the Synthesis Method of Filler on Permeability and Microwave Absorption Properties of Ferrite/Polymer Composites

Li_0.575Zn_0.4Ti_0.55Fe_1.475O₄ ferrite with the addition of 0.005 Bi₂O₃ and 0.05 MnO₂ was synthesized by the ceramic process and the glycine-nitrate process (GNP), and then used as filler in PVC polymer-based composites with variable filler volume loadings (45, 55, and 65 vol%). X-ray diffraction, scanning electron microscopy, and impedance measurement were used to analyze the structural, magnetic, and microwave absorption properties of prepared materials. The single-phase spinel structure of the ferrites was confirmed by XRD analysis. The ferrite synthesized by GNP achieved a fine-grained and more uniform microstructure. Frequency dispersion of the permeability of the composites was observed in the microwave frequency region, which was due to domain wall and natural ferromagnetic resonance. The improved return loss (RL) and the bandwidth for RL ≤ -20 dB of the composites with filler prepared by GNP are considered to be related to the increased permeability in the gigahertz band (over 1 GHz) and to a broader magnetic loss.