Dissolution and Structural Evolution of Yb2o3 in the Eutectic Lif-Ybf3 Molten Salt

Abstract

Dissolution of Yb2O3 in a eutectic LiF–YbF3 system and the structural changes in the system are key factors in efficient electrolysis in preparing rare-earth Yb alloys. In this study, isothermal saturation was used to determine the solubilities of Yb2O3 in eutectic LiF and LiF–YbF3 molten salts. The interactions between the components of the LiF–YbF3–Yb2O3 system were studied using a combination of quantum chemical calculations, thermodynamic analysis, and experimental verification. The structural evolution of the system was analyzed using high-temperature Raman spectroscopy and ab initio molecular dynamics simulations during the integration of Yb2O3 into the eutectic LiF–YbF3 molten salt. The main phases in the LiF–(21 mol.%)YbF3 system saturated with Yb2O3 consisted of LiF, LiYbF4, and a minimal amount of YbOF and its derivatives. Yb2O3 did not change the main structure of the LiF–LiYbF4 system and Li+, F−, and YbF4− were the main ionic forms in the system. The Yb–F bond in YbOF was less stable than the Yb–O bond, and YbOF easily dissociated to YbO+ and F−.

Keywords: eutectic molten salt, ab initio molecular dynamics, quantum chemical calculations, high-temperature raman spectroscopy, molten salt electrolysis