Removal of B from Si by Hf addition during Al–Si solvent refining process. Issue 1 (1st December 2016)

• Record Type: Journal Article
• Authors: Lei, Yun; Ma, Wenhui; Sun, Luen; Wu, Jijun; Dai, Yongnian; Morita, Kazuki
• Is Part Of: Science and technology of advanced materials. Volume 17:Issue 1(2016)
• Page Start: 12
• Page End: 19
• Publication Date: 2016-12-01
• Subjects: Electromagnetic solidification refining -- Al–Si solvent -- silicon purification -- hafnium addition -- boron removal; 10 Engineering and structural materials -- 106 metallic materials -- 503 TEM, STEM, SEM -- 301 chemical syntheses/processing; Materials -- Technological innovations -- Periodicals; 620.112
• DOI: 10.1080/14686996.2016.1140303
• Languages: English
• ISSNs: 1468-6996

Abstract

Abstract: A small amount of Hf was employed as a new additive to improve B removal in the electromagnetic solidification refinement of Si with an Al–Si melt, because Hf has a very strong affinity for B. The segregation ratio of Hf between the solid Si and Al–Si melt was estimated to range from 4.9 × 10 −6 to 8.8 × 10 −7 for Al concentrations of 0 to 64 at.%, respectively. The activity coefficient of Hf in solid Si at its infinite dilution was also estimated. A small addition of Hf (<1025 parts per million atoms, ppma) significantly improved the B removal. It was confirmed that the use of an increased Hf addition, slower cooling rate, and Al-rich Al–Si melt as the refining solvent removed B more efficiently. B in Si could be removed as much as 98.2% with 410 ppma Hf addition when the liquidus temperature of the Al–Si melt was 1173 K and the cooling rate was 4.5–7.6 K min –1 . The B content in Si could be controlled from 153 ppma to 2.7 ppma, which meets the acceptable level for solar-grade Si. Abstract :