Electrochemistry and electro-crystallization of yttrium on Mo substrate in LiCl-KCl eutectic salt - 5066

The electrochemistry of YCl₃ in LiCl-KCl eutectic salt was studied in the temperature range of 673-813 K by using Mo working electrode. The Y(III)/Y(0) redox reaction was evaluated with respect to its major thermodynamic, kinetic and initial electro crystallization properties. According to cyclic voltammetry and square wave voltammetry, the reduction of Y(III) ions to Y(0) metal is a one-step three-electron reaction. The equilibrium potentials of Y(III)/Y(0), determined by open-circuit chrono-potentiometry, were also used to estimate the activity coefficients of YCl₃. The limiting currents of convolutive voltammograms were employed to determine the diffusion coefficients of Y(III) ions at various temperatures. The exchange current density was determined by linear polarization of Mo electrode coated with yttrium metal. The reaction rate constant determined by convolutive voltammetry shows that Y(III)/Y(0) redox system is quasi-reversible per Matsuda-Ayabe criteria. The nucleation mechanisms of yttrium metal deposited on a Mo substrate were predicted by using Scharifker-Hill model, and verified by scanning electron microscopy (SEM), which showed that for the dilute concentration of YCl₃, yttrium nucleates and grows progressively. (authors)