The Purification Of Metallurgical Grade Silicon By Electron Beam Melting

Metallurgical grade silicon (MG-Si) is obtained from the reduction of silica (SiO 2) in a voltaic arc furnace. The impurities are inherent to the reduction process and they are also dependent on the quality of the initial materials. Among other applications, silicon is used as a substrate for photovoltaic conversion of energy and this conversion is as bigger as greater is the purity of the substrate. Researches are being carried out, in some countries, with the objective of searching for new processes of silicon purification or new materials that can be used as substrates for energy conversion. In this research, the technique of silicon purification in an electron beam furnace was used, where the melting occurs in a high vacuum and the impurities are extracted by evaporation. MG-Si in bulk form without leaching, with an initial purity of 99.88% in mass and ground and leached MG-Si, with an initial purity of 99.92%, were used as starting materials. The final purity obtained, in both materials, was above 99.999% in mass. These results demonstrate that this process is technically viable, while also eliminating the stages of chemical purification used in other techniques. © 2005 Elsevier B.V. All rights reserved.16912125Ikeda, T., Maeda, M., Purification of metallurgical grade silicon for solar grade silicon by electron beam button melting (1992) ISIJ Int., 32 (5), pp. 635-642Ikeda, T., Maeda, M., Refining of silicon for solar cells (1993) First International Conference on Processing Materials for Properties, pp. 441-445. , Honolulu, HI, USASuzuki, K., Kumagai, T., Sano, N., Removal of boron from metallurgical-grade silicon by applying the plasma treatment (1992) ISIJ Int., 32 (5), pp. 630-634Sakagushi, Y., Ishizaki, M., Kawahara, T., Production of high purity silicon by carbothermic reduction of silica using AC-arc furnace with heated shaft (1992) ISIJ Int., 32 (5), pp. 643-649Choudhury, A., Hengsberger, E., Review: Electron beam melting and refining of metals and alloys (1992) ISIJ Int., 32 (5), pp. 673-681Braga, A.F.B., Otubo, J., Mei, P.R., The electron beam melting influence on the metallurgical grade silicon purification for solar-grade silicon (1998) Proceedings of Ninth CIMTEC International Meeting, , Florence, ItalyBraga, A.F.B., Otubo, J., Mei, P.R., The purification of leached metallurgical grade silicon by electron beam melting (1998) The Third Pacific Rim International Conference on Advanced Materials and Processing, Vol. 1, pp. 1057-1062. , Honolulu, HI, USAPires, J.C.S., Upgrade of the purification of silicon through electron beam melting furnace (1999) XV COBEM - Brazilian Congress of Mechanical Engineering, , Águas de Lindóia, São Paulo, Brazil, November 22-26Pires, J.C.S., Obtaining solar grade silicon through electron beam melting (2000) CONEM-2000 - Mechanical Engineering National Congress, , Natal, RN, Brazil, August 7-11Pires, J.C.S., Profile of impurities in sample of polycrystalline silicon purified in electron beam melting furnace (2000) Proceedings of 55th Annual Congress of ABM (Brazilian Association of Metallurgy and Materials), , Rio de Janeiro, RJ, Brazil, July 24-28Braga, A.F.B., (1997) Study of the Potential of Electron Beam Melting Technique to the Metallurgical Grade Silicon Purification, 155p. , Ph.D. Thesis, Mechanical Engineering College, State University of CampinasIkeda, T., Maeda, M., Elimination of boron in molten silicon by reactive rotating plasma arc melting (1996) Mater. Trans., JIM, 37 (5), pp. 983-987Bathey, B.R., Cretella, M.C., Review: Solar-grade silicon (1982) J. Mater. Sci., 7, pp. 3077-309