Magnesiothermic Reduction of Silicon Dioxide to Obtain Fine Silicon Powder in Molten Salt Media: Analysis of Reduction Mechanism

抄録

Semiconductive silicon is widely used in solar cells, thyristors, and other important application. However, smelting and refining Si from silicon dioxide (SiO₂) still require a large amount of energy, particularly for the reduction of SiO₂ and removal of impurities. In this work, we designed an approach to prepare very fine Si powder from crystalline and/or amorphous SiO₂ through the magnesiothermic reduction of SiO₂ in molten salts. Moreover, the mechanism of reduction below 1273 K was elucidated. The composition of molten salts and the reaction temperature were varied, and their effect on the Si yield was investigated. The yield was lower in the molten NaCl-MgCl₂ molten salt solvent than in LiCl-MgCl₂, likely because of the Mg₂Si by-product formation. The higher yield in LiCl-MgCl₂ resulted from the better solubility of Mg in this molten salt and the suppression of Mg₂Si formation.