Dissolution Mechanism of YbOF in (LiF-CaF₂)_eut. Molten Salt

Abstract

The dissolution mechanism of YbOF in a fluoride-containing (LiF-CaF2)eut. molten salt is the basis for analyzing the structure of the resulting medium and optimizing the electrolytic preparation of rare-earth Yb alloys. In this study, isothermal saturation was used to analyze solubility changes of YbOF in the (LiF-CaF2)eut. system. Quantum chemical and molecular dynamics ab initio methods were used to study the basic properties of the components of the (LiF-CaF2)eut.-YbOF system and the microscopic structural changes during the dissolution process. In addition, structural changes in the YbOF-saturated (LiF-CaF2)eut. system were analyzed by combining cryogenic-temperature Raman spectroscopy with experimental methods. The results show the solubility of YbOF increased linearly in the temperature range of 1073–1323 K. As the melting temperature exceeded 1073 K, LiF and CaF2 gradually dissociated into Li+, Ca2+, and F−. In the initial stages of YbOF dissolution (1073–1173 K), the Yb–F bond was less stable than the Yb–O bond; YbOF dissociated into YbO+ and F− in this temperature range. When the temperature was increased above 1173 K, YbO+ further dissociated into Yb3+ and O2−. Overall, the dissolution of YbOF did not affect the main structure of the (LiF-CaF2)eut. system.

Keywords

• molten salt systems
• fluorine oxides
• solubility
• ab initio molecular dynamics
• high-temperature Raman spectroscopy