Electrochemical Behavior of Dysprosium in Fused LiCl–KCl Eutectic at Solid Inert Mo and Liquid Active Ga Electrodes

Abstract

Cathodic reduction of Dy3+ ions on inert Mo and active Ga electrodes in fused 3LiCl–2KCl eutectic was studied at 723–843 K in inert atmosphere by transient electrochemical techniques. It was established that the cathodic reaction on solid Mo electrode is irreversible, proceeds in one stage, and controlled by the charge transfer rate. The dependence of the apparent standard potential of Dy3+/Dy couple vs temperature was determined. The apparent standard Gibbs energy change, enthalpy, and entropy of dysprosium trichloride formation from the elements in fused 3LiCl–2KCl eutectic were calculated. The electrode reactions of the LiCl–KCl–DyCl3 solution at liquid Ga electrode were investigated by open-circuit potentiometry. The red-ox potential of the Dy3+/Dy couple on Ga electrode was observed at more positive potential values than at the inert electrode. This potential shift was thermodynamically analyzed by lowering of activity of Dy in the metal phase due to the formation of intermetallic compounds. The apparent standard potentials of Dy–Ga alloys, and the activity coefficients of dysprosium in liquid Ga based alloys between 723 and 843 K were determined. The principle thermodynamic properties of the alloys were calculated.