A DIELECTRIC MIXING LAW FOR POROUS CERAMICS BASED ON FRACTAL BOUNDARIES

The effect of porosity on tile complex dielectric permittivity of micr owave sintered zinc oxide at room temperature and 2.45 GHz is reported . The predictions of conventional Maxwell-Garnet theory and the effect ive medium approximation art in poor agreement with the experimental r esults, Various methods are employed to investigate the system in an e ffort to come up with new mixing laws, including combinations of these two analytic theories and finite difference electromagnetic simulatio ns of representative microstructures. A model that assumes the existen ce of dielectrically inactive, fractal-geometry boundaries between cer amic grains provides an excellent description of the results with no f ree parameters. It gives physical insight into the experimentally obse rved mixing law. (C) 1996 American Institute of Physics.