A Comparative Study on Ni-Zn Ferrites Via Different Synthesis Technologies Achieving Ultra-Wide Microwave Absorption Bandwidth and Ultra-Strong Microwave Absorption Capability

Abstract

Ferrites with spinel structure are widely used to solve electromagnetic radiation problems, accompanied by a trend from single materials to magnetic substrates of magnetoelectric composites. The focuses of this study are to prepare spinel Ni-Zn ferrites with superb microwave absorption performance and to analyze the electromagnetic wave absorption characteristics and interaction mechanisms to lay the foundation for synthesizing composites with more controllable properties. Significantly, the Ni 0.5 Zn 0.5 Fe 2 O 4 prepared by hydrothermal method (H-NZFO) and sol-gel auto-combustion method (S-NZFO) exhibited distinct microwave absorption properties. The S-NZFO with a thickness of 3.72 mm demonstrated the best dual-zone microwave absorption , with two strong reflection loss peaks at 5.1 GHz and 10.5 GHz, respectively, and the corresponding effective absorption bandwidth (EAB) reached 9.0 GHz, covering part of S-band and all C-band and X-band. These are attributed to the presence of high saturation magnetization, outstanding complex permeability and multiple magnetic losses. H-NZFO excelled in terms of absorption capability and matching thickness. The optimal electromagnetic wave (EMW) absorption performance of H-NZFO was that at a thickness of only 1.71 mm, the minimum reflection loss ( RL min ) reached -60.2 dB at 13.1 GHz and the maximum bandwidth corresponding to RL below -10 dB reached 4.6 GHz. These are attributed to a decrease in the size of the crystallites, a significant increase in the complex permittivity and the emergence of multiple dielectric losses. The observed ultra-wide effective absorption bandwidth of S-NZFO and ultra-strong microwave absorption capability of H-NZFO suggest that both materials have promising application prospects as substrate materials for efficient microwave absorbers in both military and civilian fields.

Keywords: Nickel zinc ferrite, Morphology, Microstructure, Microwave Absorption