High temperature calorimetric examination of enthalpies of mixing in liquid (gadolinium–germanium–manganese) alloys

Liquid alloys of (gadolinium–germanium–manganese) have been studied by a high-temperature mixing calorimetry at (T = 1830) K. The measurements have been performed along five sections with xGe:xMn = 0.25:0.75, 0.4:0.6, 0.5:0.5, 0.7:0.3, and 0.8:0.2 for 0.0 < xGd < 0.55. The integral enthalpy of mixing (ΔmixH  ) has been calculated from the experimental ΔmixH¯Gd by Darken’s equation. The values of ΔmixH have been also estimated using nine geometric models and the results of Muggianu model implementation provide the best agreement with the experimental data. Two interpolation methods have been used for describing the integral enthalpy of mixing in the ternary liquid alloys. The ΔmixH values estimated by the interpolation methods agree as well with each other as with the Muggianu model prediction. The differences between the ΔmixH values determined by experiment and from the model are small and vary from (−4.2 up to 3.5) kJ · mol−1, which is evidence for a negligibly small ternary interaction in liquid (Gd–Ge–Mn) alloys. Extreme ΔmixH values are observed in the boundary (Gd–Ge) system. Consequently, the interaction between Ge and Gd atoms make a major contribution to the thermodynamics of liquid (Gd–Ge–Mn) alloys.