Studies on slag refining and directional solidification in the purification of silicon

A new silica based slag has been developed in slag refining to reduce the aluminium concentration in solvent refined silicon. Besides aluminium, elements like Fe, V, Zr, P, etc. are reduced significantly. Directional solidification of slag refined silicon by the Bridgman crucible lowering technique has been successfully utilized to grow silicon ingots with large oriented columnar grains. An improved method of using a thin walled silica crucible with a proper backing has been developed to obtain crack-free silicon ingots