The Effect of Sc2O3 on the Physicochemical Properties of Low-Melting Cryolite Melts КF–AlF3 and КF–NaF–AlF3

Abstract

Quasibinary phase diagrams of the system “low-melting cryolite–Sc₂O₃” the potential media for synthesizing alloyed alloys Al–Sc are plotted by the method of thermal analysis. The phase diagrams of (KF–NaF–AlF₃)–Sc₂O₃ with different content of NaF and the cryolite ratio (CR) 1.3 and 1.5 are the diagrams with simple eutectics. The liquidus temperature of the (KF–AlF₃)–Sc₂O₃ system increases with the increase in the Sc₂O₃ concentration due to the formation of a high-melting compound: potassium hexafluoroscandiate К₃ScF₆. The solubility of Sc₂O₃ in low-melting cryolite melts KF–NaF–AlF₃ increases with the increase in temperature and CR. In contrast Al₂O₃, the solubility of Sc₂O₃ in melts containing KF–AlF₃ with CR = 1.3–1.5 is much lower than in cryolite melts containing NaF. The conductivity of low-melting cryolite melts measured by the method of impedance spectroscopy decreases in proportion to the Sc₂O₃ concentration in the similar way as in salt melts containing Al₂O₃. Based on the experimental data obtained, the compositions of low-melting cryolite melts are proposed for the synthesis of doped Al–Sc alloys.