Stable Hexatope LiF–LiCl–LiBr–Li2CrO4–KCl–KBr of the Li+,K+||F–,Cl–,Br–,\({\text{CrO}}_{4}^{{2 - }}\) Reciprocal Quinary System

Abstract

This paper presents a theoretical and experimental study of the Li⁺,K⁺||F^–,Cl^–,Br^–,\({\text{CrO}}_{4}^{{2 - }}\) quinary reciprocal system. А phase tree of the system was constructed. It has a branched structure and includes two stable pentatopes, a stable hexatope, and a stable tetrahedron separated by two stable tetrahedra and a secant triangle. The LiF–LiCl–LiBr–Li₂CrO₄–KCl–KBr hexatope was studied experimentally by differential thermal analysis (DTA) and X-ray powder diffraction analysis (XRD). The polythermal section passing through two low–melting quaternary eutectic points included in the boundary elements of the hexatope was studied to determine the nature of physical and chemical interactions in the hexatope. Solid solutions based on lithium and potassium chlorides and lithium and potassium bromides were found to not decompose within the hexatope. The characteristics of the composition at the minimum point in the hexatope were determined. There are four crystallizing phases in the stable hexatope: LiF, Li₂CrO₄, LiCl_xBr_1‑x, and KCl_xBr_1–x.