DILATOMETRIC AND THERMOOPTIC PROPERTIES OF ALKALINE-EARTH AND CADMIUMFLUORIDES BETWEEN 300 AND 1300-K

Temperature variation of the coefficients of linear thermal expansion and optical length was measured with an interferometer using 632.8 nm wavelength light from a He-Ne laser over the temperature range of 300- 1300 K. The experiment was carried out under a high vacuum to minimize sample oxidation. For the optical length variation, the laser beam wa s allowed to pass through the crystals while, for the thermal expansio n work, the laser beam was reflected from a coating of platinum deposi ted on the faces of crystals. Temperature variation of the coefficient of refractive index was calculated from the measurements of the coeff icients of linear expansion and optical length variation. The results were used to calculate temperature variation of the optically importan t quantities such as molecular polarizability, energy band gap, refrac tive index variation with density, and the strain-polarizability param eter with the help of the Lorentz-Lorenz relation. The optical quantit ies exhibit a small variation over the temperature range of 300- appro ximately 800 K. The results were compared to the values in available l iterature.