Effective-medium theories for spheroidal particles randomly oriented on a plane: Application to the optical properties of a SiC whisker-Al2O3 composite

A SiC whisker-Al2O3 composite was hot pressed using Al2O3 powder and SiC whiskers. Optical microscope pictures showed that the SiC whiskers are randomly oriented on a plane perpendicular to the hot-pressing direction. Infrared spectra of Reststrahlen bands of this composite were measured with four configurations. The infrared spectra demonstrate that our composite has uniaxially anisotropic optical properties. To explain the optical properties of the composite, expressions for the Maxwell-Garnett theory and the effective-medium approximation (EMA) were derived in tensorial forms. In these equations, a proper angular average was made to take into account of the preferential orientation of the spheroidal particles. Good agreement was found between the measured conductivities and the predictions of the EMA.