SiO_2飽和NaO_<0.5>-CaO-SiO_2系フラックス : 溶融シリコン間のボロンの分配挙動

概要

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In order to develop economical production process from metallurgical grade silicon to solar grade, the thermodynamics for elimination of boron, which is the most difficult impurity, in molten silicon were investigated by applying the SiO2-saturated NaO0.5-CaO-SiO2 flux system. Distribution ratio of boron between the flux and molten silicon defined by {(mass% of B in flux) / [mass% of B in silicon]} was measured at 1,723 and 1,773 K as a function of flux composition.The basicity and viscosity of the flux have a dramatic effect on the distribution behavior of boron. The maximum value of the distribution ratio of boron obtained in the present study is larger than the ones between the flux containing various alkaline-earth metal oxides and molten silicon. The obtained distribution ratio is, however, so small value (single order) that this flux treatment process cannot be directly applied to practical operation.Based on the results obtained, it was found out that there is the possibility of boron being efficiently removed from molten metallurgical grade silicon by the oxygen gas injection method using basic flux for as short operating time as possible, which can establish high basicity of flux and high oxygen partial pressure at a flux-silicon interface.
社団法人資源・素材学会の論文
2002-07-25