Research of boron removal from polysilicon using CaO-Al₂O₃-SiO₂-CaF₂ slags

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• 作者：Jiayan Li ; Lei Zhang ; Yi Tan ; Dachuan Jiang ; Dengke Wang ; Yaqiong Li
• 关键词：Boron removal ; Slag treatment ; Upgraded metallurgical grade Si
• 刊名：Vacuum
• 出版年：May, 2014
• 年：2014
• 卷：103
• 期：Complete
• 页码：33-37
• 全文大小：842 K

文摘

Purification process of MG-Si was limited by the difficulties involved in reducing boron content. The possibility of removing impurity boron (B) in MG-Si using CaO-Al₂O₃-SiO₂-CaF₂ slags was investigated in the present study. Different from traditional research methods, the whole melting process was carried out under atmosphere condition, which was closer to the actual production conditions. The thermodynamic and kinetic mechanisms of B removal were analyzed. Based on the ionic structure theory, the relation between ionic structure of slags at high temperature and optical basicity can be explained firstly. The parameters, including the slag optical basicity, melting time and CaF₂ content were discussed. The boron content was reduced from original 25聽ppmw to 4.4聽ppmw through 120聽min melting with the optical basicity of 0.551 and 5聽wt% CaF₂ additions.