Chemical equilibria between silicon and slag melts

Journal Article · Mon Aug 01 04:00:00 EDT 1994 · Metallurgical Transactions, B (Process Metallurgy); (United States)

DOI:https://doi.org/10.1007/BF02650071· OSTI ID:6960006

Weiss, T; Schwerdtfeger, K ^[1]

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1. Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. fuer Allgemeine Metallurgie

Metallurgical grade silicon is the starting material for the production of solar grade silicon and other high-purity grades. The equilibria between silicon and slags of the systems CaO-SiO[sub 2], Na[sub 2]O-SiO[sub 2], and CaO-SiO[sub 2]-Y with Y being Al[sub 2]O[sub 3], MgO, TiO[sub x], B[sub 2]O[sub 3], and Na[sub 2]O have been investigated in silica crucibles. The calcium content under silica-saturated CaO-SiO[sub 2] slag is 262 parts per million (ppm) at 1,500 C. The aluminum and magnesium contents increase with increasing alumina or magnesium oxide contents, respectively, reaching about 1,800 ppm Al at silica/mullite or about 390 ppm Mg at silica/protoenstatite saturation. Boron has a distribution ratio [B]/(B[sub 2]O[sub 3]) of 0.18. The sodium content under silica-saturated Na[sub 2]O-SiO[sub 2] slag is 25 ppm at 1,500 C. In contrast, the titanium content of the silicon, if Y is TiO[sub x] and (Ti) is in the percent range, is high and varies with the titanium content of the slag according to (wt pct Ti) = 2.7 [radical](wt pct Ti). In other experiments, it is shown that metallurgical grade (MG) silicon can be purified from aluminum, magnesium, and calcium by treatment with suitable silicate slags.

• OSTI ID: 6960006
• Journal Information: Metallurgical Transactions, B (Process Metallurgy); (United States), Journal Name: Metallurgical Transactions, B (Process Metallurgy); (United States) Vol. 25:4; ISSN MTTBCR; ISSN 0360-2141
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601* -- Other Materials-- Preparation & Manufacture
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BORON COMPOUNDS
BORON OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CONCENTRATION RATIO
DIRECT ENERGY CONVERTERS
DISTRIBUTION
ELEMENTS
EQUILIBRIUM
EQUIPMENT
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PURIFICATION
SEMIMETALS
SILICON
SILICON COMPOUNDS
SILICON OXIDES
SILICON SOLAR CELLS
SLAGS
SODIUM COMPOUNDS
SODIUM OXIDES
SOLAR CELLS
SOLAR EQUIPMENT
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS