Eur. Phys. J. Special Topics 226, 1075-1089 (2017)
https://doi.org/10.1140/epjst/e2016-60223-7

Regular Article

Thermodynamic description of the Holmium-Germanium binary system

¹ Laboratoire de Thermodynamique et Énergétique, LTE, Université Ibn-Zohr, BP 8106 Agadir, Morocco
² Laboratoire de Physicochimie de l'État Solide, ICMMO, Université Paris-Sud, 91405 Orsay Cedex, France

^a e-mail: said.kardellass@edu.uiz.ac.ma
^b e-mail: coletteservant@orange.fr

Received: 11 July 2016
Revised: 4 August 2016
Published online: 18 April 2017

Abstract

The Holmium-Germanium system was thermodynamically assessed by the CALPHAD technique based on the available experimental data including the thermodynamic properties and phase equilibria. The solution phases, i.e. liquid, hcp_A3 (Ho), and diamond_A4 (Ge), were described by the substitutional solution model with the Redlich-Kister equation, and all the intermetallic compounds HoGe_1.7 (_LT and _HT), HoGe_1.8, HoGe_2.7, Ho₁₁Ge₁₀, Ho₃+Ge₄, Ho₅Ge₄, HoGe, and HoGe_1.5(_LT and _HT) in the Holmium-Germanium system were treated as stoichiometric phases. The compound with a homogeneity range Ho₅Ge₃, is modeled using two sublattices as (Ho,Ge)_0.375(Ho,Ge)_0.625. A set of self-consistent thermodynamic parameters for the Holmium-Germanium system was finally obtained. The calculated phase diagram and thermodynamic properties agree reasonably with the literature experimental data.