Development of a Ca-K-Li-RE-Cl (RE = La, Ce, Pr, Nd) rare-earth molten salt database: RE-Cl and CaCl2-RECl3 binary systems

Abstract

During molten salt electrolysis of rare earths, the presence of multiple oxidation states of the rare earths can greatly affect Faradaic yields. The stability of these different oxidation states can be controlled by the composition of the molten salt. To assess the stability of these different oxidation states, thermodynamic modeling on the CaCl 2 -RECl 3 and RE-Cl binary systems were conducted and a database covering the binaries of the Ca-K-Li-La-Ce-Pr-Nd-Cl system was created using the two-sublattice ionic liquid model to represent the molten salt and metallic liquid in a single formalism. Electrochemical reduction potentials were computed from this database showing good agreement between experimental potentials measured against a Cl − /Cl 2 and Ag/AgCl reference electrode (computed from the AgCl-KCl-LiCl system also provided in this work).