Refining of metallurgical grade silicon by transient unidirectional solidification

The main objective of the present work is to refine metallurgical grade silicon by transient unidirectional solidification. Cylindrical ingots were obtained by melting and solidification of metallurgical grade silicon in a resistance furnace. Macro and micrographs of the longitudinal section of the ingots were examined. These reveal a grain structure consisting mainly of columnar grains and intermetallic precipitates concentrated at the ingot top. The remaining part of the ingot was free from any type of intermetallic. The compositions of samples extracted along the ingot were measured by chemical analysis, enabling the construction of concentration profiles. These profiles show an accumulation of impurity elements at the ingot top, indicating a refined silicon with lower impurity concentrations below the top.