Refining of metallurgical-grade silicon by inductive plasma
Refining of metallurgical-grade silicon by inductive plasma
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DOI：
10.1016/s0927-0248(01)00148-9
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发表时间：
2002-04
影响因子：
6.9
通讯作者：
C. Alemany;C. Trassy;B. Pateyron;K.-I. Li;Y. Delannoy
中科院分区：
文献类型：
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作者：
C. Alemany;C. Trassy;B. Pateyron;K.-I. Li;Y. Delannoy
采用感应等离子体炬与冷坩埚电磁搅拌相结合的新工艺精炼优质冶金硅。向等离子体中添加反应气体会导致液态硅表面的杂质挥发。硼杂质的浓度从原料中的15ppmw降低到等离子体处理后的小于2ppmw。硼的最易挥发的形式是BOH，其通过同时用氧和氢处理而获得。硼挥发的限制是由于在高氧气流速下在熔融硅表面形成二氧化硅层，这导致挥发速率急剧下降。与硼相反，磷的浓度仅降低了两倍，尽管其余部分似乎是电中性的。热力学研究表明，磷可以与金属杂质结合作为磷酸盐被捕获。由使用该技术生产的材料制成的电池表现出12.4%的转换效率。
A new process combining inductive plasma torch and electromagnetic stirring of molten silicon in a cold crucible has been developed to refine upgraded metallurgical silicon. The addition of reactive gases to the plasma leads to volatilisation of impurities at the liquid silicon surface. The concentration of boron impurities decreased from 15ppmw in the raw material to less than 2ppmw after the plasma treatment. The most volatile form of boron was BOH, which was obtained by simultaneous treatment with oxygen and hydrogen. The limitation in boron volatilisation is due to the formation, at high oxygen flow rate, of a silica layer at the surface of the molten silicon, which results in a dramatic drop of the volatilisation rate. In contrast to boron, the concentration of phosphorus was reduced by only a factor of two, although the remainder seems to be electrically neutral. Thermodynamic studies suggest that phosphorus could be trapped as phosphate in combination with metallic impurities. Cells made of material produced using this technique exhibited a conversion efficiency of 12.4%.