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 S iC whiskers. Optical microscope pictures showed that the SiC whiskers are randomly oriented on a plane perpendicular to the hot-pressing dir ection. Infrared spectra of Reststrahlen bands of this composite were measured with four configurations. The infrared spectra demonstrate th at our composite has uniaxially anisotropic optical properties. To exp lain the optical properties of the composite, expressions for the Maxw ell-Garnett theory and the effective-medium approximation (EMA) were d erived in tensorial forms. In these equations, a proper angular averag e was made to take into account of the preferential orientation of the spheroidal particles. Good agreement was found between the measured c onductivities and the predictions of the EMA.