L’Obtention et le Raffinage du Silicium par Voie Electrochimique

Abstract

After a brief recall starting from the discovery of silicon and pursuing up to the finding of its semiconductor properties, different methods leading to the extraction of this element are mentioned. Various processes for silicon electrowinning and most particularly those using molten salts are then described in more detail. Special reference is given to an unpublished work, regarding the solutions of silicon oxide in cryolite, carried out in this laboratory and later continued on a pilot plant.
Thermodynamic and electrochemical characteristics of the solutions of different oxides in cryolite are then examined and it is shown that in almost all cases the overall electrochemical reaction consists of a decomposition of the oxide having, at a given temperature, the less negative value of the Gibbs free energy of formation. Finally, the mechanisms of the cathodic reactions taking place during electrolysis of different molten salts are discussed.