The activity coefficients of oxygen, γo, in liquid Cu-In and Cu-Sn alloys at 1373 K have been measured over the entire composition range utilizing a modified coulometric titration method with the electrochemical cell: O in liquid Cu-In or CuSn alloys/ZrO2(+CaO)/Air, Pt. The measured In γo values, plotted in terms of indium or tin mole fraction, lie on a S-shaped curve, as predicted by Jacob and Alcock's quasi-chemical equation. The present results for Cu-In alloys were significantly different from published values, while the results for Cu-Sn alloys were in reasonable agreement with reliable published values. The interaction parameters of indium and tin on oxygen in liquid copper were evaluated from the present data for the dilute alloys to be ε0(In)=-8.9 and ε0(Sn)=-2.8 at 1373 K, respectively.
(Received July 30, 1983)
Keywords: thermodynamics of oxygen, activity of oxygen, solubility of oxygen, copper-iridium alloys, copper-tin alIoys, coulometric titration, zirconia solid electrolyte, emf measurement, solution model
* Department of Metallurgical Engineering, Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan.
** Graduate Student, Osaka University, Suita, Osaka. Present address: Sumitomo Metal Industries, Ltd., Wakayama, Japan.