Density Measurement of Molten CaF2 by an Electrostatic Levitator

High-quality single crystalline calcium fluoride (CaF2) has been of considerable practical concern as an optical lens to an excimer laser stepper in the deep-ultraviolet region due to its excellent transparency. Highly accurate thermophysical properties of molten CaF2 are essential as input data for a numerical simulation of the crystal growth process. The density of molten CaF2 has been successfully determined in the stable and undercooled liquid states (1600–1820 K) with an electrostatic levitator. The temperature dependence of the density of molten CaF2 is given by ρ/kg ·m−3 =3580−0.63T (±1.6%). The coefficient of cubical expansion of molten CaF2 has been determined to be β/K−1 = 1 5683−T .