New Mathematical Formulation for the Deposition Potential and Atomic Radius: Theoretical Background and Applications to Sn–Ln Intermetallic Compounds

Purification of rare earth elements is challenging due to their chemical similarities. The interaction and behavior of alloys involving stannous chloride (SnCl2) and lanthanide metals are discussed in the present paper. We investigate the quantitative relationship between the deposition potential of lanthanides with SnCl2 and atomic radius by employing electrochemical techniques, involving cyclic voltammetry (CV), square wave voltammetry (SWV) and open-circuit chronopotentiometry (OCP). Our electrochemical study on the formation intermetallic compounds is based on Sn in LiCl–KCl melts on molybdenum electrodes at 873 K. With the same experimental conditions, different deposits (e.g., Sn–La, Sn–Pr, Sn–Gd, Sn–Dy and Sn–Er) were obtained by using identical substrates. We establish the relationship between the deposition potential and the atomic radii of lanthanides by deriving a mathematical equation from the sorting out and summarizing of the data. The predictions for the existence and the deposition potenti...