Evaporation of phosphorus in molten silicon by an electron beam irradiation method

Kazuhiro Hanazawa, Noriyoshi Yuge, Yoshiei Kato

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

The evaporation behavior of phosphorus in molten silicon during electron beam irradiation was investigated with the aim of producing solar grade silicon (SOG-Si) from metallurgical grade silicon (MG-Si) by a sequential metallurgical process. Batch experiments showed that the evaporation rate of phosphorus increased in proportion to the power of the electron beam and phosphorus content. The phosphorus removal rate was controlled by free evaporation from the molten silicon surface. Electron beam irradiation makes it possible to secure a higher temperature at the free liquid surface, which results in more efficient dephosphorization. A continuous flow experiment indicated that the phosphorus concentration at the outlet increased when the silicon feed rate was raised, which was attributed to the fact that the hearth residence time of the molten silicon was proportionally shorter. Thus, the flow of molten silicon in the hearth did not behave as a complete mixed reactor flow type reaction, but was close to a plug flow type reaction. With a 150kg scale pilot manufacturing plant, MG-Si containing about 25 mass ppm of phosphorus was successfully purified to P < 0.1 mass ppm.

Original languageEnglish
Pages (from-to)844-849
Number of pages6
JournalMaterials Transactions
Volume45
Issue number3
DOIs
Publication statusPublished - Mar 2004
Externally publishedYes

Keywords

  • Electron beam
  • Metallurgical grade silicon
  • Phosphorus
  • Silicon
  • Solar grade silicon
  • Vacuum
  • Vapor pressure

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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