SOLUBILITY OF CARBON IN LIQUID SILICON EQUILIBRATED WITH SILICON-CARBIDE

The solubility of carbon in liquid silicon equilibrated with silicon c arbide was determined in the temperature range from 1723 to 1873 K. Si licon was melted in a silicon carbide crucible with an Ar-CO mixture g as flowing. Carbon in silicon was analyzed by the combustion-IR absorp tion method. The temperature dependence of the carbon solubility in li quid silicon can be represented by the following equation: log (C-(c u nder bar)/mass%)=3.63-9660/T(+/-0.02) (T:1723-1873 K) The carbon solub ility at the melting point of silicon was calculated to be 79 ppm (9.1 x 10(18) atoms.cm(-3)). The level of oxygen impurities in the melt wa s much lower than that of liquid silicon equilibrated with solid silic a. The standard Gibbs free energy change for carbon dissolution in liq uid silicon can be represented as: C(s)=(C) under bar C(1 mass%, in li quid silicon) Delta G degrees=7.20x10(4)-11.4Tlog T+6.20T (J).