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

Abstract

Schematic diagram of bench scale modified to allow crude directional solidification. 2 Schematic of an HEM furnace. 3 Flow diagram for refining MG silicon using an HEM furnace. 4 B reduction during refining of molten MG silicon in Experiment # 3. 5 Effectiveness of B and P removal during refining of molten MG silicon in Run # 4. Note the sudden drop in B in sample M10 and relatively no change in P concentration until directional solidification. 6 Impurity analyses of several samples taken during development of refining processes. 7 Impurity analysis for various samples in Run MG3-8. The data is normalized to initial composition to show effects of refining. Most impurities are shown using a log scale except for B and P, which are shown using a linear scale on the right side. 8 B analysis for samples from Run MG3-8 showing reduction with refining. 9 A 60-kg MG silicon charge after refining during Run MG3-10.

B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

“…The B content in typical MG-Si is between 13 and 130 ppma. [14] However, the initial B content of the Al-Si melt in this study was set to be 153 ppma (60 ppmw) considering possible contamination from Al in the practical refining process. The initial B and Zr contents of the Si-Al melt were controlled by precisely weighing the powdered Si-1 wt pct B and Si-1 wt pct Zr alloys, respectively.…”

Effects of small amounts of transition metals on boron removal during electromagnetic solidification purification of silicon with Al–Si solvent

“…The concentration of B in MG-Si has been reported to be between 13 and 130 ppma [18]. However, the initial concentration of B in the Al-Si solvent was set to 153 ppma (60 ppmw) in this study because of possible contamination from Al in an actual purification process.…”