Physicochemical analysis and structure of melts of the system LiF–NaF–K 2NbF 7

Abstract

The complex physicochemical analysis of the system LiF–NaF–K 2NbF 7, based on the phase diagram, density, surface tension, and viscosity measurements, as well as on the X-ray diffraction and IR spectroscopic analyses, was performed. The results proved that the investigated system forms a simple eutectic phase diagram with the coordinates of the ternary eutectic point 16 mol% LiF, 31 mol% NaF, 53 mol% K 2NbF 7, and t e =585 °C. The probable inaccuracy of temperature of primary crystallization in the calculated ternary phase diagram is 4.3 °C. From the molar volume, surface tension, and viscosity excesses, as well as from the X-ray diffraction and IR spectroscopic measurements of the quenched melts, it follows that the formation of the [NbF 8] 3− anions in the liquid phase was confirmed by all of the studied physicochemical parameters and is the general feature of this system.