A mathematical model for distribution of calcium in silicon by vacuum directional solidification
Calcium is one of the main impurity elements in silicon. The removal of calcium strongly affects the quality of the polycrystalline silicon ingot produced by a vacuum directional solidification method. Based on the considerations of the theory of segregation, mass transfer and evaporation...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
University of Belgrade, Technical Faculty, Bor
2016-01-01
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| Series: | Journal of Mining and Metallurgy. Section B: Metallurgy |
| Subjects: | |
| Online Access: | http://www.doiserbia.nb.rs/img/doi/1450-5339/2016/1450-53391600012Z.pdf |
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| Summary: | Calcium is one of the main impurity elements in silicon. The removal of
calcium strongly affects the quality of the polycrystalline silicon ingot
produced by a vacuum directional solidification method. Based on the
considerations of the theory of segregation, mass transfer and evaporation
during vacuum directional solidification process, a mathematical model for
calcium distribution in silicon was proposed and it can be used to explain
the removal mechanism. In order to confirm the mathematical model, an
industrial scale experiment on UMG-Si with an initial purity of 99.98 wt. %
was performed. Since the reaction temperature strongly influences both the
evaporation and segregation of calcium, the dependences of effective
segregation coefficient (keff) and the evaporation coefficient (kE) on
temperature were carefully investigated. The results showed that the proposed
mathematical model was highly consistent with the experimental data and the
calcium removal efficiency mainly relied on the evaporation step. |
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| ISSN: | 1450-5339 2217-7175 |