Cathodic processes of neodymium(iii) in LiF–NdF3–Nd2O3 melts

In this paper, cyclic voltammetry and square wave voltammetry are applied to characterize the cathode processes of neodymium ions on a W electrode in LiF–NdF3 melts with or without the metal Nd. The results indicate that neodymium ions in the LiF–NdF3 (2 wt%) melt are reduced in two steps, i.e. Nd3+ → Nd2+ and Nd2+ → Nd0, corresponding to starting reduction potentials of 0.35 V vs. Li+/Li and 0.1 V vs. Li+/Li, respectively. The Nd3+ → Nd2+ process is controlled by mass transfer and the Nd2+ → Nd0 process is controlled by both an interfacial step and mass transfer. But in the LiF–NdF3 melt with excess metal Nd equilibrium, the kinetics of the above two processes are controlled by mass transfer. After potentiostatic electrolysis at 0.35 V in the LiF–NdF3–Nd2O3 melt NdF2 is formed on the Mo cathode, and metallic Nd is obtained by potentiostatic electrolysis at 0.1 V in the LiF–NdF3–Nd2O3–Nd melt, which validates the above electrochemical reduction results.