Thermodynamic assessment of the Ho-Ga system

By means of the CALPHAD (CALculation of PHAse Diagrams) technique, the holmium-gallium binary system was critically assessed. The thermodynamic parameters involved in the excess term of the Gibbs energy phases are optimized based on all the experimental data available in the literature. The Ho-Ga system contains five intermetallic compounds: HoGa6,HoGa3,HoGa2,HoGaandHo5Ga3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HoGa}}_{6} ,\,{\text{HoGa}}_{3} ,\,{\text{HoGa}}_{2} ,\,{\text{HoGa}}\,{\text{and}}\,{\text{Ho}}_{ 5} {\text{Ga}}_{3}$$\end{document}, which are all treated as stoichiometric phases. The term exeG\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{ }<^>{\text{exe}} G$$\end{document} of the Gibbs energy of the liquid phase is described, using the Redlich-Kister, Kaptay equations and the association solution model. The primary phases alpha Ho\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha {\text{Ho}}$$\end{document} (Hcp) and Ga (orthorhombic) are treated as pure stoichiometric phases. The phase diagram and model parameters were derived from a thermodynamic optimization. More experimental work on this system may be needed to confirm our results.