Peculiarities of Holmium and Iron Triad Ions Co-Reduction: Formation of HoxNiy (HoxCoy, HoxFey) Intermetallic Compounds in Chloride Melts

The present paper is focused on the analysis of Ni2+, Co2+, Fe3+, and Ho3+ ion co-reduction in the background equimolar NaCl-KCl melt at 973 K using the method of cyclic voltammetry. It was found that the co-reduction potentials of Ho3+ and iron triad ions differ greatly. The depolarization of metallic holmium electrodeposition on one of the iron triad metals preliminary deposited on the tungsten electrode was determined. This process resulted in the formation of the HoxNiy, HoxCoy, and HoxFey intermetallic compounds. It was observed that the HoxNiy, HoxCoy, and HoxFey intermetallic compounds may be synthesized in a kinetic regime. The influence of the current density, electrolytic bath composition, and electrolysis time on the composition of the obtained intermetallic compounds was studied. The possibility of synthesizing cathode deposits composed solely of intermetallic compounds is verified. It is demonstrated that the intermetallic compounds may be formed by the addition of the iron triad metals (in particular, metallic iron) via anode dissolution. Synthesized HoxNiy, HoxCoy, and HoxFey samples were characterized by X-ray diffraction analysis, scanning electron microscopy, and photon correlation spectroscopy.