Morphological stability of solid-liquid interface during melt crystallization of M 1−x R x F2+x solid solutions

The physicochemical fundamentals of solid solutions M 1 − x R x F2 + x (where M = Ca, Sr, Ba, Cd, and R is rare-earth element) with optical quality without a growth-induced cell substructure are considered. The stability of the plane crystallization front to concentration undercooling without account of released crystallization heat is considered. A modified method of stability functions calculation of the crystallization front using phase diagrams is proposed. For MF-RF3 systems, a critical analysis of experimental data on phase equilibria in the region of existence of 55 fluorite solid solutions M 1 − x R x F2 + x is performed and the stability functions are calculated. Coefficients of cation interdiffusion in the melt are estimated by growing concentration series of single crystals.