Far-infrared investigation of the generalized Lyddane-Sachs-Teller relation using ZnS-diamond composites

Abstract

The optical properties of hot-pressed ZnS-diamond composites have been investigated in the far ir, where the wavelength is much larger than the particle size. A Kramers-Kronig analysis of the measured reflectivity in this vibrational spectral region was used to determine the dielectric function of samples with diamond volume fill fractions f as large as 55%. From these results the f dependences of two experimental quantities are determined: the ratio of the second moments of the longitudinal and transverse energy-loss functions and the ratio of the dc and high-frequency dielectric constants. Agreement with the predictions of the generalized Lyddane-Sachs-Teller relation is obtained over the entire fill-fraction range. We also find that the experimental results are compatible with those obtained within the Bruggeman effective-medium approximation.