Macrosegregation of Impurities in a Metallurgical Silicon Ingot After Transient Directional Solidification

Abstract

Metallurgical grade silicon was melted and directionally solidified in transient conditions by extracting heat from the base of a cylindrical ingot and inserting heat at the ingot top. A heat-transfer mathematical model was implemented to predict the solidification velocity and temperature gradient using cooling curves measured directly in the silicon melt. Nearly 70% of the resulting ingot displays a region of columnar grains aligned with the ingot axis. In this region, the concentration of metallic impurities is usually below the quantification limit of the analytical technique and intermetallic particles are absent, strongly indicating significant purification. The transition from the purified region of the ingot to the ingot top, where impurity concentrations increase and intermetallic particles are seen, is consistent with a change of the solid-liquid interface morphology from planar to cellular/dendritic, as similarly reported in the literature and as indicated by a preliminary analysis with the constitutional undercooling criterion.

Avaliação De Software Comercial Para Simulação CFD De Macrossegregação.

“…Como condições de contorno foram utilizadas as curvas de temperatura em função do tempo obtidas experimentalmente obtidas por Lima et al (2017). A malha utilizada foi constituída de elementos de 0,1 mm de comprimento.…”

“…Nesse trabalho, os autores testaram para diferentes condições as capacidades e limitações do módulo do FLUENT. Essa avaliação foi feita por comparação ao algoritmo desenvolvido e validado com dados experimentais e de literatura por Lima (2013) e publicados por Lima et al(2017).…”

Measurements of hardness, young s modulus, and fracture toughness of solar grade silicon obtained from metallurgical grade silicon

“…An interesting alternative route to obtain SoG-Si is the metallurgical route, which consists of refining metallurgical grade silicon (MG-Si), containing about 98.5% Si, to attain the purity of the SoG-Si. An important process step in this route is the directional solidification of the MG-Si [1][2][3][4][5] to induce segregation of metallic impurities to the silicon ingot top. Although mechanical properties of silicon play a secondary role in the efficiency of photovoltaic cells [6], its lack of ductility [7] and toughness [8] affects the production of silicon wafers and solar panels and makes the mechanical conformation of silicon practically impossible.…”