title: Preparation of high purity crystalline silicon by electro-catalytic reduction of sodium hexafluorosilicate with sodium below 180 °C.
abstract: The growing field of silicon solar cells requires a substantial reduction in the cost of semiconductor grade silicon, which has been mainly produced by the rod-based Siemens method. Because silicon can react with almost all of the elements and form a number of alloys at high temperatures, it is highly desired to obtain high purity crystalline silicon at relatively low temperatures through low cost process. Here we report a fast, complete and inexpensive reduction method for converting sodium hexafluorosilicate into silicon at a relatively low reaction temperature (∼ 200 °C). This temperature could be further decreased to less than 180 °C in combination with an electrochemical approach. The residue sodium fluoride is dissolved away by pure water and hydrochloric acid solution in later purifying processes below 15 °C. High purity silicon in particle form can be obtained. The relative simplicity of this method might lead to a low cost process in producing high purity silicon.
authors.affiliation: Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Kai
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Pu
authors.initials: P
authors.lastname: Chen
mesh_terms: D002384:Catalysis; D003460:Crystallization; D005459:Fluorides / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D012824:Silicic Acid / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D013696:Temperature
chemical_list: D012824:Silicic Acid; C004832:hexafluorosilicate; D012964:Sodium; D005459:Fluorides; D012825:Silicon