Removal of Boron from Silicon by Solvent Refining Using Ferrosilicon Alloys

The distribution of boron between purified solid silicon and iron-silicon melt was evaluated to investigate the possibility of boron removal from silicon by solvent refining with iron-silicon alloys. The distribution coefficient, defined as the ratio of the mole fraction of boron in solid to that of liquid, was found to be strongly dependent on boron concentration. Solvent refining at lower temperatures resulted in smaller distribution coefficient values. The boron removal percentages for the lowest boron concentration examined in this study were 70 pct [1583 K (1310 °C)], 65 pct [1533 K (1260 °C)], and 65 pct [1483 K (1210 °C)]. The values obtained for interaction parameter of boron on iron in solid silicon are as follows: −813 ± 53 [1583 K (1310 °C)], −830 ± 92 [1533 K (1260 °C)], −863 ± 91 [1483 K (1210 °C)]. Lower temperature resulted in smaller distribution coefficient and higher silicon yield.