The purification of metallurgical grade silicon by electron beam melting

Resumo

Metallurgical grade silicon (MG-Si) is obtained from the reduction of silica (SiO2) 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.

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