Purification of metallurgical-grade silicon using Si-Sn alloy in presence of Hf, Zr, or Ti

Hf, Zr, or Ti was employed as additive to enhance removal of the main impurities from metallurgical-grade Si (MG-Si) during the Si-Sn alloy refining process. The microstructure of Si-Sn alloy without/with Zr, Hf, or Ti was observed and analyzed by electron probe microanalysis (EPMA) to investigate the distribution of impurities. Compositions of intermetallic phases precipitated in Sn or among the grain boundaries of Si were quantitatively analyzed using EPMA. The mechanisms of their formation and the removal of impurities are discussed. The results of Si refining showed that the addition of Hf or Zr slightly enhanced the removal of Al. The high refining temperature in the Si-Sn alloy refining process was responsible for the low extraction of B. Most of Zr, Hf, or Ti was removed simultaneously with other impurities during the Si-Sn alloy refining process.