Kichiya Suzuki1, Tsuyoshi Sugiyama2, Kiyotaka Takano3 and Nobuo Sano1
1Department of Metallurgy, Faculty of Engineering, The University of Tokyo, Tokyo
The thermodynamics of the removal of boron, which is most difficult among various impurity elements, was investigated by applying the flux treatment in order to develop a new production technique of solar grade silicon (SOG-Si) by refining inexpensive metallurgical grade silicon (MG-Si).
The equilibrium distributions of boron between silicon and various fluxes CaO-SiO2, CaO-CaF2-SiO2, CaO-MgO-SiO2 (-CaF2) and CaO-BaO-SiO2 (-CaF2) systems were determined from 1723 to 1823 K under CO or Ar atmospheres. The distribution of boron has a maximum with increasing basicity and increases with raising temperature for all fluxes studied.
The reaction of the removal of boron from silicon to flux is expressed as follows;
refining, metallurgical silicon, slagging treatment, boron, thermodynamics, CaO-SiO2, CaO-CaF2-SiO_2, CaO-MgO-SiO2, CaO-BaO-SiO2
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