8. Production of scandium metal and Al-Sc alloy

Carbo-reduction in Scandinavian crucibles is chemically possible, but its high melting point (1,541°C) makes direct reduction difficult. Indeed, at this high temperature, industrial refractories are of little use (only a metal like tantalum can withstand it).

As a result, electrolysis of a mixture of molten chlorides, LiCl and KCl was adopted, giving a eutectic between 700 and 800°C. The ScCl ₃ -(LiCl + KCl) mixture is electrolyzed on a zinc cathode. The resulting Zn-Sc alloy is thermally decomposed at low pressure, with zinc volatilization. The resulting scandium metal, usually impure, containing mainly Fe and Si and various other impurities, is then evaporated under vacuum for purification.

Another interesting thermal route, which competes with the electrolytic route, which generates pollution...