Microwave Absorption Enhancement of Ni–Zn Ferrite Composites by Magnetic Nano Nife2o4 Powder Addition and Absorption Analysis According to Packing Fraction and Thickness

Abstract

The Ni 0.6 Zn 0.4 Fe 2 O 4 /NiFe 2 O 4 composite was prepared by mixing micro-sized Ni 0.6 Zn 0.4 Fe 2 O 4 (NZF) and nano-sized NiFe 2 O 4 (NF) synthesized by solid-state reaction and coprecipitation methods, respectively, with an epoxy binder. The NZF/NF was mixed at a ratio of 8/2, 6/4, 4/6, and 2/8, and the microwave absorption characteristic of each sample was investigated. The crystal structure of the synthesized powder was confirmed through X-ray diffraction analysis, and the magnetic properties were measured using a vibrating sample magnetometer. The complex permittivity and permeability of the sample were measured in the range of 1–18 GHz with a network analyzer, and the reflection losses were calculated from these measured values. The absorption bandwidth of the 3–4-mm-thick NZF/NF composite indicated a 99.9% absorption ability mainly in the C-band (4–8 GHz) and X-band (8–12 GHz), and the bandwidth of the NZF/NF composite with a thickness of less than 2 mm shifted to the Ku-band (12–18 GHz) range. In particular, it was confirmed that the absorption ability of the sample was affected by the packing fraction and magnetic properties as the sample thickness decreased. At 1.5 mm thickness, both the 6/4- and 4/6-ratio composites showed absorption peaks, whereas at 1 mm thickness, only the 4/6-ratio composite showed an absorption peak. Furthermore, the composites exhibited nearly 99.99% absorption, implying that compared to the composite containing a non-magnetic nanoferrite, the prepared sample was relatively thin and exhibited a stringer absorption.

Keywords: Spinel ferrite, Magnetic nanofiller, Packing fraction, Reflection loss, Electromagnetic absorption