Enhanced boron removal by CrMnFeNi-based high-entropy alloys during purification of silicon

Abstract

• CrMnFeNi-based HEAs was employed as a novel impurity getter for MG-Si purification. • Refined Si crystals can be better agglomerated and separated. • The maximum distribution ratio of B between alloy and Si-enriched region was 19.9. • The segregation coefficient of B in Si-HEA melts is reduced to 0.036. A novel approach is proposed to prepare high-purity Si by enhancing B removal from metallurgical-grade Si with high-entropy alloys as solvents. CrMnFeNiM (M = Al, Co, Ti, and Cu) alloy is melted with metallurgical-grade Si at 1773 K. After a period of holding time, the recrystallization of high-purity Si is realized by electromagnetic directional solidification. High-purity Si enrich in the upper region of the sample, and impurities precipitate in the bottom Si-based alloy. The enrichment percentage of Si is more than 92.9%, up to 97.4%. The maximum distribution ratio and minimum segregation coefficient of B are obtained in Si-CrMnFeNiAl solvent, which are 19.9 and 0.036, respectively. The primary cause why Si-20 at. %CrMnFeNiAl solvent stands out is that the activity coefficients of metals and B in the melt are large, which makes the formation of boride easier. This method provides a potential possibility for improving the B removal effect and reducing the cost to prepare high-purity Si.