Silicon purity controlled under electromagnetic levitation (SPYCE): influences on undercooling

The rapid evolution of photovoltaic Si production induced a shortage of high purity silicon raw material. The use of lowest purity silicon has a strong effect on the casting conditions and ingot structure and properties. During solidification, solute rejection at the growth interface leads to an inc...

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Bibliographic Details
Published in:Journal of materials science 2010-04, Vol.45 (8), p.2218-2222
Main Authors: Beaudhuin, M., Zaidat, K., Duffar, T., Lemiti, M.
Format: Article
Language:English
Subjects:
Characterization and Evaluation of Materials
Chemical Sciences
Chemistry and Materials Science
Classical Mechanics
Columnar structure
Cooling effects
Crystallography and Scattering Methods
Engineering Sciences
Grain structure
Htc2009
Impurities
Ingot casting
Ingots
Levitation
Levitation casting
Liquid phases
Magnetic levitation
Material chemistry
Materials
Materials Science
Nucleation
Partial pressure
Polymer Sciences
Purity
Silicon
Silicon carbide
Silicon nitride
Solid Mechanics
Solidification
Statistical methods
Supercooling
Undercooling
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Summary:The rapid evolution of photovoltaic Si production induced a shortage of high purity silicon raw material. The use of lowest purity silicon has a strong effect on the casting conditions and ingot structure and properties. During solidification, solute rejection at the growth interface leads to an increase of the impurities concentration in the liquid phase and then to the precipitation of silicon nitride and silicon carbide. As a consequence, the grain structure of the ingot changes from columnar to small grains, also known as grits. A new electromagnetic levitation setup which has been developed in order to measure the undercooling versus impurity concentration is presented. The impurity concentration in the levitated Si drop is controlled by the partial pressure of nitrogen or hydrocarbon gas. As nucleation is a random phenomenon, statistical measurements are presented, from samples which showed numerous heating/melting and cooling/solidification phases. The effect of carbon impurities on the undercooling of silicon droplet is discussed.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-009-4011-9