DILATOMETRIC AND THERMOOPTIC PROPERTIES OF ALKALINE-EARTH AND CADMIUM FLUORIDES 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 was allowed to pass through the crystals while, for the thermal expansion work, the laser beam was reflected from a coating of platinum deposited on the faces of crystals. Temperature variation of the coefficient of refractive index was calculated from the measurements of the coefficients of linear expansion and optical length variation. The results were used to calculate temperature variation of the optically important quantities such as molecular polarizability, energy band gap, refractive index variation with density, and the strain-polarizability parameter with the help of the Lorentz-Lorenz relation. The optical quantities exhibit a small variation over the temperature range of 300- approximately 800 K. The results were compared to the values in available literature.