Electrochemical behaviour of dysprosium(III) in LiF–CaF2 on Mo, Ni and Cu electrodes

The electrochemical behaviour of dysprosium(III) was investigated in the LiF–CaF2 eutectic mixture on molybdenum, nickel and copper electrodes in the 840–930 °C temperature range using cyclic voltammetry, square wave voltammetry and chronopotentiometry. On Mo electrode, the study showed that Dy(III) ions were reduced into Dy metal in a one-step diffusion-controlled process exchanging three electrons: Dy(III)+3e-↔Dy.Dy(III)+3e-↔Dy. The diffusion coefficients verify the Arrhenius law, allowing the activation energy to be calculated. The study of the electrochemical reduction of Dy(III) ions on reactive electrodes (Ni, Cu) first by cyclic voltammetry showed that the reduction potential of Dy(III)/Dy on reactive electrodes was observed at more positive values than those on inert electrode and then open-circuit chronopotentiometry put into evidence the formation of intermetallic compounds at more anodic potentials than pure dysprosium. Preparation of alloys layers was finally carried out by intentiostatic electrolyses at underpotential compared to the pure metal deposition; SEM observations of the layer allowed the most stable compounds prepared by this way to be identified.