Thermodynamics of the Si-Ca-O system at 1773 K

Thermodynamic properties of the Si-Ca-O System were measured by equilibrati ng molten silicon with CaO-SiO2 slags at 1773 K. Based on the results, (a) the first-order (e(O)(Ca)) and the second-order ( r(O)(Ca)) interaction parameters between calcium and oxygen, (b) the activi ty coefficient of calcium at infinite dilution referred to hypothetical liq uid in molten silicon, and (c) the standard free energy change for the diss olution reaction of calcium into molten silicon were determined to be: (a) e(O)(Ca) = -2.1(+/-0.2), r(O)(Ca) = 1.0(+/-0.1), (b) gamma(Ca(h-1))(O) = 2.4x10(-3), (c) Ca(g) = Ca (mass%, H, in Si melt): Delta G degrees/kJ = -160(+/-20), respectively, at 1773 K. By using the thermodynamic data of the Si-Ca-O system, the equilibrium rela tion between CaO and molten silicon at 1773 K was estimated.