title: Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon.
abstract: Silicon dioxide (SiO(2)) is conventionally reduced to silicon by carbothermal reduction, in which the oxygen is removed by a heterogeneous-homogeneous reaction sequence at approximately 1,700 degrees C. Here we report pinpoint and bulk electrochemical methods for removing oxygen from solid SiO(2) in a molten CaCl(2) electrolyte at 850 degrees C. This approach involves a 'contacting electrode', in which a metal wire supplies electrons to a selected region of the insulating SiO(2). Bulk reduction of SiO(2) is possible by increasing the number of contacting points. The same method was also demonstrated with molten LiCl-KCl-CaCl(2) at 500 degrees C. The novelty and relative simplicity of this method might lead to new processes in silicon semiconductor technology, as well as in high-purity silicon production. The methodology may be applicable to electrochemical processing of a wide variety of insulating materials, provided that the electrolyte dissolves the appropriate constituent ion(s) of the material.
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. nohira@energy.kyoto-u.ac.jp
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nohira
authors.forename: Kouji
authors.initials: K
authors.lastname: Yasuda
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Ito
mesh_terms: D002122:Calcium Chloride / Q000737:chemistry*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D005240:Feasibility Studies; D006358:Hot Temperature; D008422:Materials Testing / Q000379:methods; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction; D012825:Silicon / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide; D002122:Calcium Chloride; D012825:Silicon