Slag Treatment Followed by Acid Leaching as a Route to Solar-Grade Silicon

Refining of metallurgical-grade silicon was studied using a process sequence of slag treatment, controlled cooling, and acid leaching. A slag of the Na2O-CaO-SiO2 system was used. The microstructure of grain boundaries in the treated silicon showed enhanced segregation of impurities, and the formation of CaSi2 and other Ca-rich phases. Boron and...