Purification of metallurgical grade silicon by a solar process

The purification of upgraded metallurgical silicon by extraction of boron and phosphorus was experimentally demonstrated using concentrated solar radiation in the temperature range 1550–1700 °C. The process operated with a flow of Ar at reduced pressure (0.05 atm) for elimination of P, and with a flow of H2O for elimination of B. Impurity content decreased by a factor of 3 after a 50-min solar treatment, yielding Si samples with final average content of 2.1 ppmw B and 3.2 ppmw P.