Influence of CaF2 on the Liquidus Temperature and Density of the Molten (СаСl2–КCl)–CaF2 System

Influence of the CaF2 additions on the liquidus temperature and density of the molten 75.3CaCl2–24.7KCl (mol %) system has been studied. The system in question is a promising media for the innovation technology of electrolytic calcium production. The liquidus and solidus temperatures of the quasi-binary [75.3CaCl2–24.7KCl]–CaF2 system were determined within the CaF2 concentrations range from 0 to 36 mol % using the thermal analysis. The eutectic point was found at 12.7 mol % CaF2 and 903 K. The [75.3CaCl2–24.7KCl]–CaF2 system has a wide homogeneous area of the liquid state, which verifies the possibility of using it as an electrolyte in the electrochemical technologies, where CaF2 concentration reaches 15–20 mol % at the temperatures of 920–940 K. Density of molten system [75.3CaCl2–24.7KCl]–CaF2 was measured by the hydrostatic weighing technique using the experimental installation located in the glove box with inert atmosphere; the CaF2 concentration in the melt was not exceeding 36 mol % in the temperature range of 920–1090 K. Linear equations for the density temperature dependence were obtained. The dependence density–CaF2 concentration in the melts containing different amount of CaF2 as well as the dependence density–molar volume have a nonlinear character. The deviations from linearity are observed for the melts containing more than 12.7 mol % CaF2 at 973 K, which may be associated with the changes in the melt structure at the increase in content of the fluorine ions, which have large ionic moment.