Study On The Activity Of Impurity Components In Silicon Fluid Based On Thermodynamic Model

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,?NiAl=-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,?MnFe=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.