Solubility of RE 2 O 3 (RE = La and Nd) in light rare earth fluoride molten salts

The chemical reaction and dissolution processes of RE2O3 in REF3-LiF (RE = La and Nd) molten salts were studied by X-ray diffraction, differential thermal analysis and chemical analysis. Firstly, RE2O3 disperses in molten salts and reacts with REF3 and LiF, which lead to the generation of a new phase REOF, resulting in the dissociation or formation of complex ions by part of REOF, and the sedimentation of excessive REOF at the bottom. The RE contents in molten salts were used to determine the solubility of RE2O3. The results show that with 20 mol%–40 mol% of REF3, the solubility ranges from 1.79 to 3.05 g RE2O3 per 100 g electrolyte and the corresponding mole concentration is 0.33%–0.87%. RE2O3 solubility increases with increasing temperature and REF3 concentration. The natural logarithm of the RE2O3 solubility is plotted against 1/T and can be interpreted by linear relationship. The fitting parameters can be used to estimate the solubility of RE2O3 with minimized experimental efforts and difficult experiment conditions.