Partition of the Quaternary Reciprocal System Na,Rb||F,I,CrO4 and Investigation of the Stable Tetrahedron NaF–RbI–RbF–Rb2CrO4

Abstract

The quaternary reciprocal system Na,Rb||F,I,CrO₄ was studied, low-melting mixtures based on which are promising as fusible electrolytes for chemical current sources, heat-storage materials, and media for growing single crystals. The system was partitioned into simplexes using graph theory, and the tree of phases of the system was constructed. The tree of phases is linear and contains four stable tetrahedra sharing stable cutting triangles. The combined stable tetrahedron NaF–RbI–RbF–Rb₂CrO₄ was investigated by differential thermal analysis. The crystallization surface of this stable tetrahedron is represented by the volumes of sodium fluoride, rubidium iodide, rubidium fluoride, rubidium chromate, and the compound Rb₃CrO₄F. Monovariant equilibrium lines meet at two quaternary invariant points: eutectic E^◻491 and peritectic P^◻508.