Study on redistribution of boron during silicon solidification refining process in Si–Al melts

Abstract

Redistribution of boron during the silicon solidification refining process using an Si–Al melt has been studied by electron probe microanalysis and inductively coupled plasma mass spectrometry. The results and the effects of alloy composition, cooling rate and heating method on boron removal indicate that silicon can be purified by the segregation of boron to the α-Al component of the eutectic phase after the alloy solidification. Furthermore, use of lower cooling rate and Si–Al alloy with low Si content shows enhanced boron redistribution. The lowest refining ratio (0·17) and the highest removal fraction of boron (74·3%) were achieved in 22·8 at-%Si–Al alloy at a cooling rate of 3 K min⁻¹. Induction heating was used to obtain agglomerated Si plates and also recycled ∼73·9% (by area) of byproduct (i.e. Si–Al alloy) from 35·4 at-%Si–Al alloy.

Keywords:

• Metallurgical grade silicon
• Boron redistribution
• Alloy solidification refining
• Si–Al alloy melt
• Solar power