熔盐电解-区域熔炼法制备太阳能级硅的工艺研究

Process for Solar Grade Silicon Production by Molten Salt Electrolysis and Zone Melting

以高纯石英为原料,石墨坩埚和钨为电极材料,在CaCl2-LiCl混合熔盐(摩尔比9∶1)中电解制备Ca-Si合金,经区域熔炼提纯制得太阳能级硅(SG-Si)。用XRD,SEM和ICP-MS对电解合金及提纯后产物进行表征和含量分析。结果表明:在电解槽电压2.6V、温度850℃的条件下,产物为Ca-Si合金。经过两次区域熔炼提纯后,硅锭85%以上的区域纯度接近99.9999%,符合SG-Si的要求。

Ca-Si alloys were prepared in molten CaCl2-LiCl（mole ratio of 9∶1）with high purity silicon dioxide as raw material,high purity graphite and tungsten as electrode by an electrolysis method.The solar grade silicon（SG-Si）was got after the alloys purified by zone melting process.The alloy and purified production were characterized by X-ray diffraction（XRD）,scanning electron microscope（SEM）and inductively coupled plasma mass spectrometry（ICP-MS）.The results show that electrolysis product is alloy of calcium and silicon at 850℃ when the cathodic voltage is about 2.6V.After twice zone melting process,the purity of silicon of 85%silicon ingot as-prepared is nearly 99.9999%,complying with the standard of SG-Si.