Facile Electrochemical Preparation of Al-Sm Alloys in Molten Calcium Chloride

The direct preparation of metallic Sm or alloys from raw oxide Sm2O3 is an attracting but challenging process. The stable electrochemical behavior and low solubility of Sm2O3 limit the extraction of Sm element in molten salts. Here, it is found that metallic Sm is hardly obtained by electro-deoxidation and aluminothermic reduction of solid Sm2O3 pellet according to experiment and calculation. Through the novel electrochemical reduction of solid Sm2O3-Al pellet, Al3Sm alloy with ∼0.4 Sm/Al molar ratio is successfully prepared in calcium chloride melt at 1173 K. The reduction potential of Sm2O3-Al pellet to Al-Sm alloy is more positive than that of calcium. Al plays an indispensable role in the reduction of Sm2O3. The preparation process of alloy can be well identified as two steps: Sm(III) → Sm(II) and Sm(II) → Sm(0). Sm2O3 is firstly converted to Sm(II) based on the combination of electrochemical and aluminothermic reduction. Then, Al3Sm is formed by electrochemical reduction and alloying with Al.