2018 年 86 巻 4 号 p. 198-201
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.