基于热力学模型的硅液中杂质组元活度研究

【作者】 于强；

【导师】 马文会； 伍继君；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2017， 硕士

【摘要】 与传统能源相比,太阳能发电具有清洁节约、安全便捷、资源丰富等优点,是可再生的绿色环保能源。太阳能多晶硅(SOG-Si)是太阳光电转化的关键材料,具有制备工艺相对成熟、生产成本低及电池产品稳定等优点。目前,采用湿法冶金、合金精炼、真空精炼等方法提纯冶金级硅的冶金法由于建设周期短、生产能耗低、污染低等众多优点受到普遍关注。冶金法的各项工艺与硅熔体中各结构单元的热力学性质息息相关,但由于高温测定实验难度大造成相关工作严重不足。因此,通过模型模拟的方法获得Si基二元及多元体系的热力学性质将有很大的现实意义与指导价值。将获得的计算数据与文献报道值进行对比,验证了模型及方法的有效性与可靠性,为Si基熔体的热力学描述及冶金法提纯多晶硅奠定理论基础。本文采用MIVM模型计算了 Si-j(j=B、Mn、Ni)二元Si基熔体各组元的活度、无限稀活度系数等热力学性质,获得了 1700-1900K温度范围内,Si-j(j=B、Mn、Ni)二元Si基熔体中组元j的自相互作用系数等热力学数据。基于以上结果,进一步计算了三元Si基熔体:Si-Fe-j(j=Al、B、Mn)、Si-Al-Ni各组元的活度,获得了 1750-1900K温度范围内,Si-Al-Ni三元Si基熔体中A1与Ni的交相互作用系数与温度的表达式:εNiAl=-1.5136+5482.8088/T,以及1700-1900K温度范围内Si-Fe-Mn三元Si基熔体中Fe与Mn的交相互作用系数与温度的表达式:εMnFe=1.8825+2891.0303/T,并绘制了各体系的三元等活度相图。基于共存理论模型计算了 Si-j(j=P、Al、Fe、Ca)二元Si基熔体各结构单元的活度等热力学性质,获得了 1723-1873K温度范围内,Si-j(j=P、Al、Fe、Ca)二元Si基熔体中组元j的自相互作用系数等热力学数据。基于以上结果,计算了三元Si基熔体:Si-Fe-j(j=Ca、P)各结构单元的活度,获得了 1723-1873K温度范围内,Si-Fe-j(j=Ca、P)两个三元Si基熔体中组元Fe.与组元j(j=Ca、P)间的交相互作用系数与温度的关系表达式,并绘制了各体系的三元等活度相图。通过热力学推导发现,在1723K温度条件下,Si-Fe-Ca三元硅基熔体中杂质Ca(500-2500ppmw)的活度小于 CaSi 和 CaSi2 的活度,Fe(500-1500ppmw)的活度小于FeSi和FeSi2的活度,且CaSi2的活度大于CaSi,FeSi2的活度大于FeSi。更多还原

【Abstract】 Compared with traditional energy,solar energy have many advantages such as cleanness,high efficiency,safe and convenient,abundant resources,etc.Solar grade silicon(SOG-Si)is one of the key materials for solar photoelectric conversion due to its comparatively mature technology,low manufacture cost,excellent product property.The purification method of industrial grade silicon include hydrometallurgy,solvent refining and vacuum refining,which have attracted much attention because of their short production period、low-cost and lower pollution.The process of metallurgical method is closely related to the thermodynamic properties of the structure unit in silicon melt,but the thermodynamics data of Si-based melt is woefully inadequate ascribed to rigorous experimental conditions.With this background,this paper establishes prediction model of thermodynamics properties for silicon solutions by means of computer-aided calculation,which is very valuable in practicality and guide.The validity and reliability of this model is verified by compared with the reported experiment data from literature,which will lay the foundation for the description of thermodynamics properties of silicon solutions and the knowledge of purifying polysilicon.In this paper,the molecular interaction volume model(MIVM)was used to calculation the activities and infinite dilution activity coefficients of Si-j(j=B,Mn,Ni)binary solutions.The relations between self-interaction parameters of B,Mn,Ni in dilute silicon solutions and temperature at the range of 1700-1900K is also obtained.Based on the above results,the activities of impure components has been obtained from the Si-Fe-j(j＝Al,B,Mn)systems as well as Si-Al-Ni ternary solutions.The interaction parameters between Al and Ni in dilute silicon solutions of Si-Al-Ni at the range of 1700-1900K are also investigated,εNiAl=-1.5136+5482.8088/T.The same happens with Fe and Mn in Si-Fe-Mn solutions,the interaction parameters between Fe and Mn was calculated,εMnFe=1.8825+2891.0303/T.In addition,the ternary phase diagram of various systems were also obtained.On the basis of coexistence theory model,this paper focuses on the activities and infinite dilution activity coefficients of Si-j(j＝P,Al,Fe,Ca)binary solutions,and the self-interaction parameters of P,Al,Fe,Ca in dilute silicon solutions at 1723-1873K also were calculated.According to the above results,the activities of impure components in Si-Fe-j(j=Ca,P)ternary solutions as well as the interaction parameters between Fe and Ca,Fe and P in dilute silicon solutions at 1723-1873K were tried through the use of model.Meanwhile,the iso-activity phase diagrams at 1723K were obtained.During thermodynamical deducing,it is found that the activity of the Ca impurity(500-2500ppmw)in Si-Fe-Ca ternary system was less than that of CaSi and CaSi2 at the temperature of 1723k.At the same situation,the activity of Fe impurity(500-1500ppmw)was less than that of FeSi and FeSi2.Moreover,the activity of CaSi2 was larger than that of CaSi,the relationship of FeSi2 to FeSi was the same as CaSi2 to CaSi.更多还原