Effect of Heating Rate on the Refining of Metallurgical-Grade Silicon during Fractional Melting

Silicon was purified using fractional melting (FM), which is a more effective refining method than fractional solidification. Changes in the silicon microstructure during FM were observed using a scanning electron microscope (SEM) and an electron probe microanalyzer (EPMA). Purity of each sample was investigated using inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the effects of various heating rates on the efficiency of FM. A refining ratio of 97.28% was the best result that could be obtained for the sample that was heated at a rate of 15 degrees C/min. For the samples that were heated below 1390 degrees C lower heating rate resulted in higher refining efficiency. Acid-leaching yielded 99.98% pure silicon samples after FM. (C) 2013 The Japan Society of Applied Physics