Modeling of the Phase Assemblage of the LiF–Li2CrO4–LiRbCrO4–LiKCrO4 Stable Tetrahedron of the Li+, K+, Rb+||F–, Quaternary Reciprocal System

Abstract

Here, phase equilibria in a quaternary reciprocal system comprised of fluorides and chromates of lithium, potassium, and rubidium was studied. The phase assemblage of the system was partitioned to stable simplices. The Li–Li2CrO4–LiRbCrO4–LiKCrO4 stable tetrahedron was selected as the subject matter of this study due to its undoubted scientific importance. The analysis of the boundary elements predicted, and the DTA experimental study of phase equilibria in the system proved, that monovariant phase equilibrium L ⇄ LiF + α-Li2CrO4 + (LiKxRb1 – xCrO4)ss is realized in the system, described by line Е 397–Е 400; the characteristics of the minimum point of this monovariant equilibrium (Min◻ 367) were elucidated. The mass balance of the phase reaction for this point is presented. A 3D model of the phase assemblage of the system was designed based on experimental data. The system preserves the continuity of (LiKxRb1 – xCrO4)ss solid solutions. The mixture whose composition corresponds to point Min◻ 367 has a relatively low melting temperature and can serve as a material for new fusible electrolytes in chemical current sources; it can also be of interest as an electrolytic bath for recovery of metals from melts.