Removal of B from Si by solidification refining with Si-Al melts

To discuss the removal of B by solidification refining of Si with a Si-Al melt, the segregation of B between solid Si and the Si-Al melt was investigated by use of the temperature-gradient-zone melting (TGZM) method. The segregation ratio of B at its infinite dilution was determined to be 0.49 (1473 K), 0.32 (1373 K), and 0.22 (1273 K), respectively. With the obtained segregation ratio, the activity coefficient of B in solid Si at its infinite dilution relative to pure solid B was determined by the following equation: Calculated results of directional solidification of the Si-Al alloy revealed the removal fraction of B to be as much as 90 pct. The effective removal of B by a solidification refining process with a Si-Al melt is clarified.