Abstract
We developed a composite conductor-backed single layered electromagnetic wave absorbers of composite materials (spinel-type Ni-Zn ferrite, SiO2) which can operate in the frequency region between 1 and 10 GHz. Both the complex permittivity and the complex permeability for the composite ferrite obeyed Lichtenecker's logarithm mixed law. A composite ferrite with a suitable thickness have the higher absorption frequency range than both Ni-Zn ferrites and Ba ferrite absorbers. The center absorbing frequency can be changed by changing the mixing ratio of SiO2, the thickness, or the composition of Ni and Zn. The absorption band width is almost independent on the thickness of the composite ferrite in the wide frequency range. The range of absorbable thickness becomes wider than that of Ni-Zn ferrite. The density and the hardness is improved by adding B2O3. The conductance value, however, increases and the center absorbing frequency is shifted to the lower frequency in proportional to the density. The conductance value can be reduced by adding a small amount of CoO.
