Grain-size Dependence of Absorption Characteristics of the Electromagnetic Wave Absorbers of Ferrite-SiO2 Composites

Abstract

Grain-size dependence of electromagnetic absorbing characteristics for composite materials made of Ni-Zn ferrite and SiO2 was investigated by using SiO2 with various grain sizes (29µm, 30nm, 12nm, 7nm). The absorption characteristics of ferrite composites using SiO2 of the average grain size 30nm, 12nm or 7nm were improved compared with those of ferrite composites using SiO2 of the average grain size 29µm in the low frequency region. Furthermore, grain size dependence for composite materials of Mn-Zn ferrite with the average grain size of 130nm and SiO2 with the average grain size of 29µm was investigated. The absorbing center frequency was shifted to the higher frequency region compared with that of Mn-Zn ferrite. © 2003, The Institute of Electrical Engineers of Japan. All rights reserved.