Physicochemical Investigation of the Ternary (LiF + MgF2)eut + LaF3 Molten System

The physicochemical properties of the (LiF (1) + MgF2 (2))eut + LaF3 (3) molten system have been investigated. The phase equilibria, density and volume properties, electrical conductivity, and surface tension have been selected for investigation. The phase equilibria have been measured by thermal analysis method, and the CALPHAD method for optimizing of the phase diagram has been used in order to interpret the obtained experimental data. Calculated values of the eutectic point of the binary system (LiF (1) + MgF2 (2))eut have the following coordinates: eutectic temperature T eut = 998 K and x 2 = 0.3095 and calculated composition of the ternary eutectic, according to the thermodynamic model, are at x 1 = 0.6627, x 2 = 0.2718, and x 3 = 0.0655. The Archimedean method of hydrostatic weighing was used for density measurements, a method based on the principle of phase shift measurement was used for electrical conductivity measurements, and the maximum bubble pressure method was used for surface tension measurements. The calculated concentration dependencies of particular physicochemical properties showed increasing character for density, partial molar volume, and electrical conductivity, while decreasing character was observed for surface tension. These data have been compared with corresponding physicochemical properties of two other molten systems: (LiF + CaF2)eut + LaF3 and (LiF + NaF)eut + LaF3.