The electrochemical formation of Dy-Ni alloys was investigated in molten CaCl 2 -DyCl 3 (1.0 mol%) at 1123 K. Cyclic voltammetry indicated the formation of Dy-Ni alloys at more negative than 1.0 V vs. Ca 2+ /Ca. Higher cathodic currents were observed from approximately 0.6 V, which indicated the formation of Dy-Ni alloys having higher Dy concentration. An opencircuit potentiometry was carried out with Mo and Ni electrodes before and after the addition of DyCl 3 . After the potentiostatic

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... lysis of Mo electrode at −0.50 V for 30 s in molten CaCl 2 -DyCl 3 , only one potential plateau appeared at 0.33 V, which was interpreted as the equilibrium potential of Dy 3+ /Dy. In contrast, four potential plateaus were observed at 0.49, 0.62, 0.87, and 1.04 V for Ni electrode after the potentiostatic electrolysis at 0.25 V for 15 min. According to energy-dispersive X-ray spectroscopy and X-ray diffraction of the electrolyzed samples, the four potential plateaus correspond to the two-phase coexisting states of (DyNi + DyNi 2 ), (DyNi 2 + DyNi 3 ), (DyNi 3 + DyNi 5 ), and (DyNi 5 + Ni). Standard Gibbs energies of formation were calculated for Dy-Ni alloys.