Study on columnar crystal growth in directional solidification for solar grade silicon produced by metallurgical route
Directional solidification is one of important steps to produce solar grade silicon from metallurgical grade silicon via metallurgical route and control the columnar crystal growth besides purification effect. In this paper, pilot-scale experiments in directional solidification furnace to control growth of the columnar crystal were investigated via optical microscopy images and electron back scattered diffraction (EBSD). The results showed that all large-size columnar crystals grew along directional solidification orientation and were perpendicular to the bottom of graphite crucible at the cooling rate 15 μm/s and EBSD results illustrated that the small-angle grain boundaries accounted for 1.5% and the Σ3 grain boundaries accounted for 14.7%.