Growth of congruently melting Ca0.59Sr0.41F2 crystals and study of their properties

Homogeneous crystals of Ca0.59Sr0.41F2 alloy (sp. gr., Fm 3 m, a = 0.56057 nm), corresponding to the point of minimum in the melting curve in the CaF2-SrF2 phase diagram, have been grown by the vertical Bridgman method. The optical, mechanical, electrical, and thermophysical properties of Ca0.59Sr0.41F2 and MF2 crystals (M = Ca, Sr) have been studied and comparatively analyzed. Ca0.59Sr0.41F2 crystals are transparent in the range of 0.133–11.5 μm, have refractive index n D = 1.436, microhardness H μ = 2.63 ± 0.10 GPa, ion conductivity σ = 5 × 10−5 S/cm at 825 K, and thermal conductivity k = 4.0 W m−1 K−1 at 300 K. It is shown that the optical properties of Ca0.59Sr0.41F2 crystals are intermediate between those of CaF2 and SrF2, whereas their mechanical and electrical characteristics are better than the latter compounds.