title: Removal of B from Si by Hf addition during Al-Si solvent refining process.
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 × 10-6to 8.8 × 10-7for 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.
authors.affiliation: State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming650093, PR China;; National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming650093, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Lei
authors.affiliation: State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming650093, PR China;; National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming650093, PR China.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Ma
authors.affiliation: National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology , Kunming 650093 , PR China.
authors.forename: Luen
authors.initials: L
authors.lastname: Sun
authors.affiliation: National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology , Kunming 650093 , PR China.
authors.forename: Jijun
authors.initials: J
authors.lastname: Wu
authors.affiliation: National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology , Kunming 650093 , PR China.
authors.forename: Yongnian
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo , Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Morita
keywords: 10 Engineering and structural materials; 106 metallic materials; 301 chemical syntheses/processing; 503 TEM, STEM, SEM; Al–Si solvent; Electromagnetic solidification refining; boron removal; hafnium addition; silicon purification