Density and surface tension of molten calcium fluoride

The density and the surface tension of molten calcium fluoride have been measured in the temperature range from 1690 to 1790 K by an improved Archimedian method and a ring depressing technique (J. Crystal Growth 187 (1998) 391), respectively. The ring depressing technique was demonstrated as an effective technique to measure the surface tension in comparison with the conventional ring pulling technique. The density varied with the temperature change corresponding to a linear relationship: ρ=3.767?6.94×10^?4T (K). The density of the CaF₂ melt at the melting point is 2.594 g/cm³, which is equal to the result obtained by Shiraishi and Watanabe (Bull. Res. Inst. Miner. Dressing Metal, Tohoku Univ. 34 (1978) 1), but the temperature coefficient of the density is different from the results obtained by other investigators. The thermal expansion coefficient of calcium fluoride melt linearly increases with temperature heating. The surface tension of molten calcium fluoride indicates a negative linear relationship as a function of the melt temperature: γ(T)=442.4?0.0816×T(K) (mN/m). The surface tension measured using the ring depressing technique is larger than those results obtained by other techniques.