日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 2 (1990),
pp. 168-172

Thermodynamics for Removal of Boron from Metallurgical Silicon by Flux Treatment

Kichiya Suzuki1, Tsuyoshi Sugiyama2, Kiyotaka Takano3 and Nobuo Sano1

1Department of Metallurgy, Faculty of Engineering, The University of Tokyo, Tokyo
2Department of Metallurgy, Faculty of Engineering, The University of Tokyo, Tokyo. Present address: Recruit Co. Ltd., Tokyo
3Department of Metallurgy, Faculty of Engineering, The University of Tokyo, Tokyo. Present address: Shin-etsu Chemical, Co. Ltd., Isobe

Abstract:

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;


(Received 1989/8/24)

Keywords:

refining, metallurgical silicon, slagging treatment, boron, thermodynamics, CaO-SiO2, CaO-CaF2-SiO_2, CaO-MgO-SiO2, CaO-BaO-SiO2


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