Electrochemical Formation of Nd–Ni Alloys in Molten CaCl₂–NdCl₃

Abstract

The electrochemical formation of Neodymium–Nickel (Nd–Ni) alloys was investigated in a molten CaCl 2 –NdCl 3 (1.0 mol%) system at 1123 K. Cyclic voltammograms for Molybdenum (Mo) and Ni electrodes showed the electrodeposition/dissolution of metallic Nd and the formation/dissolution of Nd–Ni alloys, respectively. The equilibrium potential of Nd 3+ /Nd was determined at 0.27 V (vs. Ca 2+ /Ca) by open-circuit potentiometry for a Mo electrode. The potentials of 0.48, 0.68, and 0.95 V, corresponding to the two-phase coexisting states of (NdNi 2 + NdNi 3 ), (NdNi 3 + NdNi 5 ), and (NdNi 5 + Ni), respectively, were confirmed using energy-dispersive X-ray spectroscopy and X-ray diffraction of the Ni electrode electrolyzed samples. The optimum electrolysis conditions for the Nd and Dysprosium (Dy) separation were discussed, and the standard Gibbs energies of formation were calculated for Nd–Ni alloys.