Fundamental Aspects of Silicon Refining

硅是制造太阳能电池的主要材料，占当今光伏材料市场的90%以上。然而，硅的有限供应和高昂的价格为实现该技术成为主要电力生产商的潜力制造了一个主要障碍。这主要是因为目前没有以可接受的成本和较高的生产率生产太阳能级硅(SOG-Si)的专用工艺。在过去的几年里，我们的可持续材料加工研究小组与其他几个小组一直在努力开发与今天的工艺相比，能够以更低的成本生产SOG-Si的技术。这类研究工作的重点大多是通过实验工作开发工艺，然后进行优化，在尽可能短的时间内达到工业规模。与任何其他发展一样，对优化技术至关重要的基本方面往往没有得到详细的研究，在几个案例中。通过这项发现拨款，将对几种硅提纯技术的基本方面进行调查。特别是，与硅精炼热力学有关的四个主题是令人感兴趣的，并将被研究：(A)杂质(P和B)在固体硅和含铁、铜、锌的二元硅合金之间的分布；(B)含各种氧化物的炉渣和在一定氧势下的渣-金属之间杂质分布的热力学；(C)含硅(含铜、铝)的合金和熔盐之间P和B分配的热力学；以及(D)二氧化硅在冰晶石熔盐中的溶解度。这类研究对于支持先前与开发SOG-Si生产技术有关的活动至关重要。此外，这些基础研究对于在用火法冶金技术处理高纯硅这一相对年轻的领域建立知识库至关重要。长期的好处是通过推进太阳能领域的发展来产生清洁能源，并培养几名在材料加工、能源材料和表征领域具有专业知识的研究生和本科生。

Silicon is the primary material for manufacture of solar cells, accounting for over 90 percent of today's market for photovoltaic (PV) materials. Nevertheless, the limited supply and high price of Si have created a major obstacle to realizing the technology's potential for becoming a major electricity producer. This is chiefly because currently there is no dedicated process for production of solar grade silicon (SoG-Si) at acceptable cost and high production rate. In the past several years, our Sustainable Materials Processing Research Group, along with several other groups have been striving for developing technologies that would produce SoG-Si at a lower cost compared to today's processes. Most of the emphasis in such research works has been development of process(es) through experimental work followed by optimization, that will reach commercial scale in the shortest time possible. Similar to any other development, often the fundamental aspects that are essential to optimizing the technology have not been looked into, in details in several cases. Though this discovery grant, the fundamental aspects of several silicon purification techniques will be investigated. In particular, four topics related to the thermodynamics of Si refining are of interest and will be studied (a) distribution of impurities (P and B) between solid silicon and binary silicon alloys with Fe, Cu, and Zn, (b) thermodynamics of impurity distribution between slag and metal for slags containing various oxides and under a range of oxygen potentials, (c) thermodynamics of P and B distribution between alloys of Si (with Cu, Al) and molten salt, and (d) solubility of silica in cryolite based molten salts. This kind of research is essential in supporting the previous activities related to developing a technology for generation of SoG-Si. In addition, such fundamental studies are critical in creating a knowledge base in the relatively young field of high purity Si processing by pyrometalllurgical techniques. The long term benefits are generation of clean energy through advancing solar energy field, and training several graduate and undergraduate students with expertise in the fields of materials processing, energy materials, and characterization.