Calorimetric studies and thermodynamic properties of liquid Ag–Ca alloys

Highlights: • Calorimetric measurements of liquid Ag–Ca alloys. • Integral enthalpies of mixing of liquid Ag–Ca alloys at T = (1131 and 1254) K. • Thermodynamic properties of liquid Ag–Ca alloys. - Abstract: Integral molar enthalpies of mixing were determined by drop calorimetric method for Ag–Ca liquid alloys at temperatures (1254 and 1131) K using a Setaram MHTC 96 Line evo calorimeter. Measurements were conducted for alloys of concentrations between 0.0642 ⩽ X_Ca ⩽ 0.9396 at T = 1254 K and at 1131 K between 0.7564 ⩽ X_Ca ⩽ 0.9647. The obtained values are negative in the entire range of concentrations and the minimum of the integral enthalpy of mixing equal –24609 J/mol of atoms was observed for 0.4634 mol fraction of calcium at T = 1254 K. The analysis of experimental data showed that most probably ΔH_m of Ag–Ca liquid alloys is independent of temperature and that they are almost twice less exothermic than those ones by the partial pressure measurements. Based on the data of this study and that available in the literature, the interaction parameters of Redlich–Kister equation for the liquid Ag–Ca phase were evaluated. The concentration fluctuation structure factor Scc(0) calculated using drawn up in this study equation showed the swallow minimum between Ca concentrations appropriate for Ag₉Ca₂ and AgCa intermetallic phases what can suggest at two kind of associates in liquid solutions