Predicting the Dielectric Properties of Mixtures: A Practical Engineering Approach
J. P. Calame,1 Y. Carmel,1 D. L. Gershon,1 and M. Rosen2
1Institute for Plasma Research, University of Maryland, College Park, Maryland 20742, USA 2
Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
Invited Talk, First World Congress on Microwave Processing
Lake Buena Vista, Florida, January 5-9, 1997
ABSTRACT. When two or more materials are combined to form an inhomogeneous mixture, predicting the dielectric properties of the mixture in terms of the properties of the constituents can be a challenging task. Equations which attempt to make such predictions are known as mixing laws, and many different mixing laws have been developed over the last 100 years. In general it is necessary to know something about the microstructure of the material in question to decide on which mixing law to use, and even if the microstructure is known there are limits on the range of dielectric permittivities and relative concentrations over which the mixing law applies. The presentation will show that in fact only a relatively small number of different mixing formulae are really needed for many applications. For cases that are not covered by the most common analytic equations, personal computer-based simulations using finite difference techniques can be used instead. Practical implementations of these methods will be discussed, along with examples from a variety of microstructures. A particularly important use of the computer methods is to ascertain which analytic formula most closely approximates the physical, realistic microstructure system. Correct determination of this functionality allows subsequent computations to be performed analytically, with a significant savings of time.