Reinvestigation of the DyCl3–LiCl binary system phase diagram

A Dańczak,L Rycerz

doi:10.1007/s10973-016-5547-y

Abstract

The phase equilibria in the DyCl3–LiCl binary system were established on the basis of differential scanning calorimetry (DSC) measurements. One compound, namely Li3DyCl6, is formed in this system. It melts congruently at 768 K with enthalpy of 51.6 kJ mol−1. DSC curves for eutectic composition and for compositions close to eutectic (on the left and right side of eutectic) are identical. Small effect related to the liquidus is shadowed by a big effect related to eutectic, and only one thermal effect is visible. This is the reason that eutectic composition can not be determined directly. The only possibility to determine it precisely is a creation of Tammann diagram. Two eutectics, namely LiCl–Li3DyCl6 and Li3DyCl6–DyCl3, located at DyCl3 mol fractions x = 0.206 (T = 746 K) and x = 0.542 (T = 674 K) were found from Tammann’s plots, which predict, through application of the lever rule, the variation of the enthalpy associated with eutectic melting as a function of composition.

Highlights

Rare-earth halides are used in a number of applications such as reprocessing of nuclear wastes, recycling of spent nuclear fuel [1], doses in high-intensity discharge lamps, lasers and new highly efficient light sources with energysaving features [2, 3]
The phase equilibria in the DyCl3–LiCl binary system were established on the basis of differential scanning calorimetry (DSC) measurements
Pioneering works devoted to the phase diagrams of lanthanide chloride–alkali metal chloride systems were performed in the sixties of the twentieth century mainly at the Lomonosov University in Moscow [5]

Summary

Introduction

Rare-earth halides are used in a number of applications such as reprocessing of nuclear wastes, recycling of spent nuclear fuel [1], doses in high-intensity discharge lamps, lasers and new highly efficient light sources with energysaving features [2, 3]. The above examples confirm the statement about serious errors and lack of precision of existing phase diagrams of lanthanide chloride–alkali metal chloride binary systems that have been published in the literature. According to the literature data [16], the DyCl3–LiCl system is characterized by the existence of Li3DyCl6 compound that undergoes a solid–solid phase transition at 743 K and melts incongruently at 748 K.

Results

Conclusion