Electromagnetic characterization of fine-scale particulate composite materials

We report the results of the composition and frequency-dependent complex permittivity and permeability of ZnO and gamma-Fe2O3 composites prepared by powder pressing. The electromagnetic properties of these materials exhibit a strong dependence on the powder size of the starting materials. In the microwave frequency range, the permittivity and permeability show nonlinear variations with volume fraction of Fe2O3. As the particle size decreases from a few micrometers to a few tens of nanometers, the data indicate that local mesostructural factors such as shape anisotropy, porosity and possible effect of the binder are likely to be intertwined in the understanding of electromagnetic properties of fine-scale particulate composite materials. (C) 2002 Elsevier Science B.V. All rights reserved.