Determination of microwave complex permittivity of particulate materials

A practical method for determining the broadband microwave complex permitti vity of particulate materials is described. In this method, particulate mat erials are dispersed randomly in paraffin wax; thin disc samples are prepar ed for measurement from the particle-wax mixtures. During measurements, the samples are backed by a conducting plane, and an open-ended coaxial probe is used to determine the permittivity of the samples. A mixture equation is used to calculate the permittivity of the particulate materials from the p ermittivity of the samples. The validity of six well known mixture equation s is examined. The experimental results indicate that only the QCA-CP and B ruggeman mixture equations can accurately describe the microwave permittivi ty of the particle-wax mixtures over the wide particle concentration range. To validate this described method, the complex permittivities of PbTiO3 an d Pb(Zr0.53Ti0.47)O-3 particles are determined over a frequency range of 0. 2 to 6 GHz. The determined results are found to be in agreement with the co axial transmission/reflection measurement results. The advantages and limit ations of this method are also discussed in this paper.