Mass spectrometric determination of ternary interaction parameters of liquid Cu–In–Sn alloy

The vaporisation of a liquid Cu–In–Sn system has been investigated between 1273 and 1473 K using Knudsen effusion mass spectrometry (KEMS) and the data obtained fitted to a Redlich–Kister sub-regular solution model. We examined 23 different compositions at four fixed indium concentrations: xIn = 0.20, 0.25, 0.29, 0.30 and 0.40 and evaluate the thermodynamic activities of all three components, not by applying the standard KEMS pressure calibration procedure, but from the measured ion intensity ratios of Cu+ to Sn+ using a recently published mathematical regression technique. The intermediate data obtained directly from the regression technique are the Redlich–Kister ternary L-parameters that are, as a function of temperature, as follows:L0 = (−59473 ± 7057) + (726.8 ± 42.3)·T − (89.0 ± 5.1)·T·ln(T);L1 = (156840 ± 5.2E − 9) − (80 ± 3.3E − 11)·T − (5.57E − 11 ± 4E − 12)·T·ln(T);L2 = (−137168 ± 8819) + (592.4 ± 52.9)·T − (70.6 ± 6.4)·T·ln(T).By using these values together with binary parameters taken from the literature, we were able to calculate several other thermodynamic functions of mixing. In particular, the partial heat of mixing of indium and its activity, which we evaluated and compared with the measured values along the Cu/Sn = 1 isopleths. We obtained a good agreement between the calculated and measured values for partial heats while in the case of activity a good agreement between the two data sets is limited to a lower mole fraction of indium.