Recherches sur le raffinage électrolytique du silicium

Abstract

Silicium can be purified electrolytically either from solid silicium or from a molten alloy of SiCu, using a solution of silica in cryolith as electrolyte. The purity of Si obtained lies between 99,7y0 and 99,99%.

Silicon Electrochemistry in Molten Salts

“…Early works reported electrochemical Si refining in a solution of SiO 2 in cryolite (Na 3 A1F 6 ) at 1000 °C, purification in a liquid state at 1427 °C in BaO–SiO 2 –BaF 2 melt, and temperature lowering to 750 °C using the KF–LiF–K 2 SiF 6 electrolyte . In recent years, recovery of Si from the Si–4.7Fe alloy was achieved by selective Si electro-dissolution in molten NaF–KF at 850 °C .…”

Structural correlations and chemistry of the Na3AlF6 − SiO2 melt as an electrolyte for the solar grade silicon (SOG − Si) electrowinning

“…Previous screening in between the several molten salt electrolytes has pointed out that, with respect to the deposited material purity and process current efficiency, the cryolite-based melts are promising media for the electrowinning of silicon [22][23]. The process has not yet been, however, successfully commercialized due to the rather high melting point of silicon (1412 °C), prohibiting the production of liquid primary silicon at the temperatures usual for cryolitic electrolytes (ca 1000 °C).…”

Improving Purity and Process Volume During Direct Electrolytic Reduction of Solid SiO2 in Molten CaCl2 for the Production of Solar‐Grade Silicon

“…[4][5][6][7][8][9] Various new electrochemical methods are promising candidates for producing SOG-Si. [10][11][12][13][14][15] Typically, electrochemical production methods are classified as either (A) electrodeposition from Si II or Si IV ions supplied as additives [12][13][14] or (B) electrorefining low-purity Si or Si-based anodes. [10,11,14,15] We have been studying the direct electrolytic reduction of solid silicon dioxide (SiO 2 ) to Si in molten calcium chloride (CaCl 2 ) at 1123 K as a new electrochemical method.…”

“…[10][11][12][13][14][15] Typically, electrochemical production methods are classified as either (A) electrodeposition from Si II or Si IV ions supplied as additives [12][13][14] or (B) electrorefining low-purity Si or Si-based anodes. [10,11,14,15] We have been studying the direct electrolytic reduction of solid silicon dioxide (SiO 2 ) to Si in molten calcium chloride (CaCl 2 ) at 1123 K as a new electrochemical method. [16][17][18][19][20][21][22][23] Silicon production by the electrochemical reduction of SiO 2 in molten salt was also reported by other groups.…”