Electrochemical Behavior of Dy(III) and Mg(II) and Co-deposition of Dy–Mg Alloy in Molten Fluoride Salts

Cyclic voltammogram, square-wave voltammogram, and open-circuit chronopotentiometry were used to study the electrochemical behavior of Dy(III) in LiF–DyF₃ melts, Mg(II) in LiF–MgF₂ melts and their co-deposition in LiF–DyF₃–MgF₂ melts at 1273 K on a Mo electrode. It is found that the reduction of Dy(III) is reversible with a one-step transfer of three electrons. The diffusion coefficient of Dy(III) in the molten fluoride salt at temperature of 1273 K is 1.18 × 10⁻⁸ cm² s⁻¹. A Dy–Mg intermediate compound co-deposition peak was observed in molten LiF–DyF₃–MgF₂ melts. All Dy–Mg intermediate alloys were prepared in LiF–DyF₃–MgF₂–Dy₂O₃–MgO molten salts by galvanostatic electrolysis at a cathodic current density of 4 A cm⁻² for 1 hour with different raw material (Dy₂O₃ and MgO) mass ratios (4.66:1 and 2.33:1) and electrolysis temperatures (1273 K and 1323 K) on the Mo electrode. A series of characterization methods including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the Dy–Mg intermediate alloys. The above characterization results show that Dy is first precipitated on the Mo electrode at 1273 K, and then Mg is deposited on it by underpotential deposition to form Dy–Mg alloy dominated by DyMg phase and Dy0.7Mg0.3 phase.