The oxygen solubility in liquid silicon equilibrated with solid silica
(cristobalite) was determined in the temperature range between 1693 a
nd 1823 K. Silicon was melted in a silica crucible with oxygen gas flo
wing. Oxygen in a quenched sample was analyzed by the inert gas fusion
-IR absorption method. The optimum furnace power and bath composition
for oxygen extraction were determined. The temperature dependence of o
xygen solubility in liquid silicon could be expressed as the following
equation. log (C-O under bar/mass%)= -4620/T+0.332(+/-0.06)(T:1693 si
milar to 1823 K) The oxygen solubility in liquid silicon at the meltin
g point (1685 K) was calculated to be 39 ppm (3.4 x 10(18) atoms . cm(
-3)). Using the temperature dependence of oxygen solubility in the pre
sent work and the standard free energy of formation of silica in the l
iterature, the standard free energy change follows: 1/2O(2)(g)=(O) und
er bar(mass%, in liquid silicon) Delta G degrees= -3.88 x 10(5)+95.6 T
(J) According to the previously reported correlations between the stan
dard enthalpy change for oxygen dissolution in liquid metals and the s
tandard enthalpy of the formation of the metal oxides at 298 K per mol
of oxygen, and the standard enthalpy change and the standard entropy
change for oxygen dissolution in liquid metals, it was suggested that
the present Delta G degrees value, i.e., the oxygen solubility in liqu
id silicon, was reasonable.