Composite Electromagnetic Wave Absorber Made of Ni-Zn Ferrite Particles Dispersed and Isolated in an SiO<sub>2</sub> Medium

Abstract

In order to design a ferrite absorber that can be used at frequencies of several GHz, the frequency dependences of the relative complex permeability μr*, the relative complex permittivity εr*, and return loss were investigated for a composite made of Ni-Zn ferrite and SiO2. When ferrite particles were dispersed and isolated in an SiO2 medium, the frequency dependence of μr* was different from that for a composite made of SiO2 particles dispersed and isolated in the ferrite medium. Moreover, when ferrite particles were isolated and a suitable mixture ratio of ferrite and SiO2 was selected, the return loss was less than −20 dB at frequencies of several GHz. The dispersion states of ferrite and SiO2 particles are thus important factors to design an absorber, and improvement in the absorption characteristics of the ferrite tile which is used as a practical absorber could be achieved using a composite made of Ni-Zn ferrite particles dispersed and isolated in an SiO2 medium.