Solubility of Carbon in Liquid Silicon Equilibrated with Silicon Carbide

Abstract

The solubility of carbon in liquid silicon equilibrated with silicon carbide was determined in the temperature range from 1723 to 1873 K. Silicon was melted in a silicon carbide crucible with an Ar-CO mixture gas flowing. Carbon in silicon was analyzed by the combustion-IR absorption method. The temperature dependence of the carbon solubility in liquid silicon can be represented by the following equation:
log(C_C⁄mass%)=3.63−9660⁄T(±0.02) (T: 1723-1873 K)
The carbon solubility at the melting point of silicon was calculated to be 79 ppm (9.1×10¹⁸ atoms·cm⁻³). The level of oxygen impurities in the melt was much lower than that of liquid silicon equilibrated with solid silica. The standard Gibbs free energy change for carbon dissolution in liquid silicon can be represented as:
C(s)=C(1 mass%, in liquid silicon)
ΔG°=7.20×10⁴−11.4TlogT+6.20T (J)