Autor(es)

Martorano, M. A. ^[1] ; Ferreira Neto, J. B. ^[2] ; Oliveira, T. S. ^[1] ; Tsubaki, T. O. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Met & Mat Engn, BR-05508900 Sao Paulo - Brazil

^[2] Inst Technol Res, Lab Met & Ceram Mat, BR-05508901 Sao Paulo - Brazil

• Tipo de documento: Artigo de Revisão
• Fonte: MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS; v. 176, n. 3, p. 217-226, FEB 25 2011.
• Citações Web of Science: 97

Resumo

The directional solidification of a typical and a previously refined metallurgical silicon was carried out in a vertical Bridgman furnace. The mold velocity out of the hot zone of the furnace changed from one experiment to another in the range between 5 and 110 mu m s(-1). Samples were extracted from the cylindrical ingots obtained in the experiments to investigate the effects of the mold velocity on the micro and macrostructures and on the concentration profiles of impurities along the ingots. At the lowest mold velocity, the macrostructures consist of columnar grains oriented approximately parallel to the ingot axis. As velocity increases, grains become thinner and more inclined in the radial direction. Precipitated particles containing Si, Fe, Al, and Ti are observed at the top of all ingots and, as the mold velocity increases, they are also seen at the ingot bottom and middle. The concentration profiles of several impurities have been measured along the ingots by inductively coupled plasma atomic emission spectrometry (ICP), indicating an accumulation of impurities at the ingot top. Consequently, the bottom and middle of the ingots are purer than the corresponding metallurgical silicon from which they solidified. Slices from the ingot bottom have also been analyzed by the glow discharge mass spectrometry technique (GDMS), allowing measurement of impurity concentrations that were below the quantification limit of the ICP. The purification effect and the accumulation of impurities at the ingot top are more pronounced as the mold velocity decreases. In the ingots obtained from the typical metallurgical silicon at the lowest mold velocities (5 and 10 mu m s(-1)), except for Al, all impurities are in concentrations below an important maximum limit for the feedstock of solar grade silicon. At the same mold velocities, the concentrations of Fe, Ti, Cu, Mn, and Ni measured at the bottom of the ingots obtained from both types of metallurgical silicon (typical and previously refined) are even below some limits suggested directly for solar grade silicon. (C) 2010 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 03/14118-1 - Refino do silicio por solidificacao direcional.
• Beneficiário: Joao Batista Ferreira Neto
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 03/08576-7 - Modelagem matemática da solidificação de ligas binárias sob efeito de convecção natural no líquido e movimentação da fase sólida
• Beneficiário: Marcelo de Aquino Martorano
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores