Aluminothermic Reduction of Quartz Sand

Development of Solar Grade (SoG) Silicon

“…It has been recognized that, other than B, P and Al, most impurities can be reduced sufficiently using directional solidification. Upgrading MG silicon in the past has included using high-purity starting materials during MG silicon production, hydro-, pyro-metallurgical refining, high-vacuum refining and plasma-arc reduction of impurities prior to directional solidification of molten charge [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . None of these processes has reached commercialization because B and P could only be removed using special processes that were not cost Final Report for DOE SBIR Phase II, Contract Number DE-FG02-04ER83928 Crystal Systems, Inc., 27 Congress Street, Salem, MA 01970 effective.…”

Production of Solar Grade (SoG) Silicon by Refining Liquid Metallurgical Grade (MG) Silicon: Final Report, 19 April 2001

“…This material after refining showed that its B content was reduced by several orders of magnitude, to ~1 ppma (0.4 ohm-cm, or about 5x10 16 cm -3 ). NREL's Silicon Materials Research team grew and wafered small <100> dislocation-free Czochralski (Cz) crystals from the new feedstock material for diagnostic tests of electrical properties, C and O impurity levels, and PV performance relative to similar crystals grown from EG feedstock and commercial Cz wafers.…”

“…Several approaches to upgrade MG silicon 7 in an arc furnace were pursued in Germany, but these efforts were curtailed without commercialization. Similarly, other approaches [8][9][10][11][12][13][14][15][16][17][18][19][20] did not result in a product.…”

Production of solar grade (SoG) silicon by refining liquid metallurgical grade (MG) silicon: Annual Report: June 10 1998--October 19, 1999

“…Several approaches to upgrade MG silicon 7 were pursued in Germany to upgrade in an arc furnace, but these efforts were curtailed without commercialization. Similarly, other approaches [8][9][10][11][12][13][14][15][16][17][18][19][20] did not result in a product.…”