Simultaneously removal of P and B from Si by Sr and Zr co-addition during Al–Si low-temperature solvent refining

To remove the key impurity elements,P and B,from primary Si simultaneously,Sr and Zr co-addition to Al-Si alloy systems during solvent refining has been investigated.Sr reacts with Al,Si,and P in the melt to form a P-containing Al_(2)Si_(2)Sr phase and Zr reacts with B to form a ZrB_(2) phase.In the Al-Si-Sr-Zr system,high removal fractions of P and B in the primary Si,with 84.8%-98.4%and 90.7%-96.7%,respectively,are achieved at the same time,respectively.The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000μg·kg^(-1),and the removal fractions of P and B in the purified Si reach 98.4%and 96.1%.Compared with the Sr/Zr single-addition,the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend,indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent.Finally,an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases,which reveals the interaction between the impurity phases and the primary Si.

Recent progress in upgrading metallurgical-grade silicon to solar-grade silicon via pyrometallurgical routes

Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.