Separation and purification of silicon by combined Si-Sn alloy refining and directional solidification process

The directional solidification of Si-Sn melt was carried out by controlling the temperature gradient and the moving velocity of thermal field in the ingot furnace. The morphology characteristics, structure and purification effect of the silicon ingot were studied. The results indicate that the growth of bulk Si is achieved from Si-Sn melt, and a flat and stable phase interface forms between the silicon and solvent by directional solidification, resulting in an effective separation. Meanwhile, purification of the refined Si by acid-leaching shows that metallic impurities decrease from 58.3×10-6 to 7.6×10-6, and the removal rate reaches 87%. Non-metallic P content decreases from 50.12×10-6 to 8.48×10-6, and the removal rate is over 80%. Therefore, not only the effective separation of silicon and solvent, but also the efficient removal of impurities is realized through Sn-Si alloy refining and directional solidification process.