ABSTRACT. The complex permittivity of alumina composites was measured and modeled with respect to the concentration of lossy additions (copper oxide or SiC), preparation method (ball milling or chemical precipitation), and density. The complex permittivity was measured in a nondestructive resonance cavity. Dielectric mixing laws and computer simulations were used to estimate the effective permittivity of these composite systems. By incorporating physically realistic ceramic microstructures, our simulations accurately modeled multicomponent systems. Most significantly, the loss tangent of the alumina/copper oxide composites was affected by particle size and the distribution and structure of lossy inclusions. These models can be extended to a variety of composite systems.

Work supported by AFOSR, Ceramic Materials Program.

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