Thermodynamic Properties of Alloys in the Binary Ca–Ge System

Mixing enthalpies of the liquid alloys in the binary Ca–Ge system were measured by isoperibolic solution calorimetry within the concentration ranges 0 < xGe < 0.08 at 1270–1300 K, and 0.54 < xGe < 1 at 1370–1520 K. The experimental data show great exothermic effects of alloy formation; the partial mixing enthalpies at infinite dilution of the components are ΔH¯Ca∞\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Delta \overline{H}_{\text{Ca}}^{\infty } $$\end{document} = −138 to −140 kJ mol−1 and ΔH¯Ge∞\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Delta \overline{H}_{\text{Ge}}^{\infty } $$\end{document} = −200 kJ mol−1 (at 1300 K). The Gibbs energies and entropies of mixing, activities of the components, and molar fractions of associates in the melts were calculated over a wide temperature range, using models of ideal and regular associated solutions, according to the data in literature for the thermodynamic properties of solid alloys and the phase diagram of the Ca–Ge system.