Molten salt electrolysis of neodymium: electrolyte selection and deposition mechanism

Molten salt electrolysis of neodymium from Nd2O3 can be a viable alternative to calciothermic reduction. Two important issues merit attention: selection of an appropriate electrolyte and the mechanism of the neodymium deposition reaction. Cyclic voltammetry experiments and melting point considerations point to the eutectic LiF-CaF2 as an appropriate electrolyte. The presence of CaF2 polarises the Li deposition reaction to more cathodic potentials, thereby providing a larger potential window for the deposition of neodymium. Experiments with the LiF-CaF2-NdF3-Nd2O3 and LiF-CaF2-LaF3-Nd2O3 melts suggest that both [NdF6](3-)and [NdOF5](4-),depending on their molar ratios, can be reduced to neodymium.