Spatial inhomogeneity in crystalline materials and saddle-type congruent melting points in ternary systems

Solidification of multicomponent melts to solid solutions is considered in terms of thermodynamic topological analysis. The use of phase portraits of systems for finding congruent melting points (invariant points) is discussed. Methods for predicting the existence of invariant points in ternary systems are considered. An example analysis is presented for two series of fluoride systems (CaF₂–SrF₂–RF₃ and SrF₂–BaF₂–RF₃, where R are rare-earth elements). The stability of melt crystallization in the vicinity of congruent melting singular points of solid solutions is discussed. The bibliography includes 104 references.