Thermophysical Properties of Single Crystals of CaF2–SrF2–RF3 (R = Ho, Pr) Fluorite Solid Solutions

Single crystals of Ca 1 – y Sr y R х F 2 + х (R = Ho, Pr) solid solutions with high optical quality have been grown by the Bridgman technique in vacuum using a fluorination atmosphere. The thermal conductivity of the Ca 0.60 Sr 0.40 – х Ho х F 2 + х solid solutions decreases from 3.27 to 2.37 W/(m K) as the fraction of holmium rises from 0 to 3 mol %, respectively. The room-temperature thermal conductivity of the Ca 0.50 Sr 0.50 – х Pr х F 2 + х solid solutions decreases from 3.38 to 2.18 W/(m K) as the fraction of praseodymium rises from 0 to 8 mol %, respectively. Increasing the holmium and praseodymium content of the ternary solid solutions leads to a gradual increase in their refractive index. With increasing wavelength, the refractive index gradually decreases.