Thermodynamic properties of the liquid Ge-Cu and Ge-Au systems by mass spectrometry

Abstract

The activities and partial molar heats of mixing have been determined for the liquid Ge-Cu system at 1525°C and the liquid Ge-Au system at 1400°C. The experimental technique consisted of analyzing Knudsen cell effusates with a TOF mass spectrometer. The ion current ratios for the monomeric vapor species were measured as a function of temperature and composition and the thermodynamic properties calculated using a modified form of the Gibbs-Duhem equations. Both systems exhibited negative deviations from ideal behavior. The results for the Raoultian activity coefficients can be partially represented by

$$\begin{gathered} \log \gamma _{Ge} = - 2.521X_{Cu}^2 + 0.948 (0 \leqslant X_{Ge} \leqslant 0.2) \hfill \\ \log \gamma _{Cu} = - 0.048X_{Ge}^2 - 0.466 (0 \leqslant X_{Cu} \leqslant 0.2) \hfill \\ \end{gathered} $$

for the Ge-Cu system at 1525°C and by

$$\begin{gathered} \log \gamma _{Ge} = - 2.327X_{Au}^2 + 0.465 (0 \leqslant X_{Ge} \leqslant 0.35) \hfill \\ \log \gamma _{Au} = - 0.510X_{Ge}^2 - 0.489 (0 \leqslant X_{Au} \leqslant 0.30) \hfill \\ \end{gathered} $$

for the Ge-Au system at 1400°C. An experimental technique is presented for determining the contribution of dissociative ionization of polymer species to the measured monomeric ion current ratio . The effect of dissociative ionization of the germanium polymer species present in the Knudsen ceil effusate was determined to be negligible.