湿法提纯制备太阳能级硅过程的研究

Hydrometallurgical purification process for preparing solar-grade silicon

采用盐酸和氢氟酸两步法湿法提纯制备太阳能级多晶硅,当工艺条件为w(HCl)=8%,w(HF)=6%,可使铁中杂质质量分数降到26×10-6,去除率达到99.1%;铝中杂质质量分数降低到60×10-6,去除率为82.3%。分析和讨论了酸浸过程中硅晶体的形貌和结构的变化。FESEM图像表明杂质在硅的表面呈现集中链状分布,晶粒沿着高应力和缺陷区直线式分裂;XRD数据显示,在反应过程中,杂质的析出对硅晶格结构的影响有限,晶格因温度增加、应力不平衡等因素反而呈现膨胀的趋势。研究和分析湿法冶金中硅晶体结构和形貌的变化,对于了解酸浸过程反应机理,提高湿法提纯的除杂效率,优化太阳能级硅生产工艺具有重要意义。

Using hydrochloric acid and hydrofluoric acid as leaching agents,a two-step method was introduced to prepare solar-grade silicon through hydrometallurgical route.The result shows that when the silicon powder is leached at appropriate condition of w（HCl）=8%,w（HF）=6%,the impurities mass fraction of Fe is reduced to 26×1 0-6 , with the removal rate of 99.1%;the impurities mass fraction of Al is reduced to 60 ×1 0-6 ,with the removal rate of 82.3%.The changes in the morphology and crystalline structure of Si during the leaching process were discussed. The images of FESEM show that the impurities are in line-like centralized distribution on the surface of Si crystal. The crystalline grain splits directly along the area where the stress is strong and which contains numerous defects. XRD data indicate that the impurities dissolved out of Si have little effect on the crystalline structure,whereas the crystal expands as a result of temperature rise and unbalance of stress.Analyzing the variation of morphology and crystalline structure of silicon is of great importance to understand the mechanism of leaching process,improve the purification efficiency and optimize the industrialized technology for preparing solar-grade silicon.