Cathodic Behaviour Of Samarium(â…¢) And Sm Alloys Preparation In Fluorides Melts

The electrochemical behavior of samarium ions in LiF-CaF2 melts at tungsten electrodes was investigated by cyclic voltammetry and square wave voltammetry. The apparent equilibrium constant of Sm(â…¡) and Sm(â…¢) at different temperature and LiF effects were studied for the first time. The results were as follows:(1) The electrochemical reduction of Sm(â…¢) into Sm in the melts proceeded according to a two-step process. The first step Sm3++e-â†'Sm2+ was reversible, but the second step was not observed in cyclic voltammograms due to a more negative reduction potential than that of Li(â… ) ions.(2) The results from cyclic voltammograms and square-wave voltammograms have proved that Sm and Al ions could be co-reduced from LiF-CaF2-AlF3-SmF3 melts.The cathodic products from galvanostatic electrolysis on a Mo electrode in LiF-CaF2-Sm2O3 (0.15mol/L)-AlF3(8.89mol/L)and LiF-CaF2-Sm2O3(0.225mol)-AlF3(0.296mol/L)-Al(6mol/L) melts were mainly composed of Al, Al2Sm and Al3Sm.(3) The equilibrium between metallic Sm and Sm ions in LiF-CaF2 melts at various temperature as well as LiF effects on the equilibrium have been first investigated. The reliable equilibrium constants Kc are calculated by the best-fitting method under the consideration of the SmOF formation and dissolution, which are 3.49 at 1123 K,2.67 at 1173 K and 1.95 at 1233 K. With the increasing of the concentration of Li(â… ) in the melts, The average valence of samarium ions decreases and therefore, the Kc values reduces accordingly.