Research on new method of electron beam candle melting used for removal of P from molten Si

Abstract

A new method, electron beam candle melting (EBCM), is proposed for the removal of P in molten Si, to produce high quality material such as solar grade silicon for photovoltaic applications. EBCM is designed to overcome the shortcomings of electron beam melting while utilising the high saturated pressure of P in molten Si to effect refining. The experimental result showed that it could remove P from Si effectively; in addition, the energy utilisation ratio was experimentally proved to be high. The evaporation coefficient of P removal is in a reasonable region and comparable with the theoretical value, which indicates that EBCM is a feasible method for the removal of P in molten Si in low power.

Research on the Influence of Electron Beam Parameters on Molten Pool Morphologies during Electron Beam Melting Silicon

“…During electron beam melting or vacuum melting, P is removed by evaporation from the molten surface to the vacuum. The removal efficiency can be improved by scattering the electron beam to the molten surface to form a shallow molten pool [9] . Zheng et al [10] studied the relationship between the ratio of diameter to height and the impurities removal efficiency.…”

Progress in Research and Development of Solar-grade Silicon Preparation by Electron Beam Melting

“…电子束熔炼的原料来源于前端的定向凝固, 需 要对定向凝固的铸锭进行破碎, 前后环节之间衔接 性差, 增加了工艺流程。Jiang 等 [43][44][45] 结合电子束熔 炼和凝固的特征, 提出了一种小功率、浅熔池的熔 炼技术, 即电子束烛光熔炼技术, 利用电子束圆形 波扫描所形成的具有最大表面积和最浅熔池深度的 无 机 材 料 学 报 第 30 卷 图 7 0.5 kg 的硅在电子束熔炼时的参数优化结果 [42] Fig . 7 The optimum value of melting parameters for 0.5 kg silicon by electron beam melting [42] 临界熔池状态 [46] 。在对杂质蒸发和分凝耦合理论进一步 完善的基础上 [47][48] , 研究了杂质在电子束诱导定向 凝固铸锭中的分布。这类杂质在铸锭中具有明显的 分凝效应, 分凝作用将杂质推到硅熔体中, 提高硅 熔体中杂质浓度, 促进蒸发作用下杂质的去除效果, 相比于完全的蒸发提纯过程, 当总时间一致时, 电 图 8 小功率、浅熔池熔炼方式示意图 [44] Fig.…”