Effect of mechanical stirring on silicon purification during Al-Si solvent refining

Abstract

Al-Si solvent refining is a promising method to purify silicon, and boron and phosphorus are key impurity elements to be eliminated. When primary silicon grows in hypereutectic Al-Si melt, impurity atoms are enriched at the solid-liquid interface and diffuse into the remaining melt. Mechanical stirring was introduced in the Al-Si solvent refining in this work to dilute the concentrated impurity atoms at the solid-liquid interface. A rotating tube with an end closed was used to stir the Al-Si melt. It is found that mechanical stirring is beneficial to impurity atoms removal. Boron and phosphorus contents in purified silicon with mechanical stirring are smaller than that without mechanical stirring. When stirring speed increases, boron and phosphorus contents in purified silicon decrease.