Bismuth germanate single crystals containing low angle and

Various formulae appearing in the literature for the permittivity of heterogeneous mixtures consisting of spherical metal particles dispersed in a dielectric base medium have been tested. Bruggeman's equation was found to be the most satisfactory.Based on the formula of Morabin, Tete and Santini for pure dielectric heterogeneous mixtures, a successful permittivity relation for conductor-dielectric mixtures has been derived for metal particles of specific shapes. The relation reduces to Bruggeman's relation for spherical particles. By following De Loor's procedure for determining specific particle shapes, the formula has been successfully tested for iron particles dispersed in mineral oil.

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By using the double-ellipsoid model of Bilboul, two theoretical expressions have been derived for correlation of the permittivity of a heterogeneous mixture with the permittivities of its components for specific particle shapes. One of the equations is identical to that of Morabin et al (1967) derived under different considerations. Both the expressions were found to give good dielectric correlation for lamellar-shaped glass particles dispersed in nitrobenzene.

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