Thermodynamic properties of liquid silver–gallium alloys determined from e.m.f. and calorimetric measurements

The thermodynamic properties of the liquid Ag–Ga alloys were determined using e.m.f. and calorimetric methods. In the e.m.f. method, solid oxide galvanic cells were used with zirconia electrolyte. The cells of the type W,AgxGa(1-x),Ga2O3//ZrO2+(Y2O3)//FeO,Fe,W were used in the temperature range from 1098 K to 1273 K, and in the range of mole fraction from xGa = 0.1 to xGa = 1.0.At first, the Gibbs free energy of formation of pure solid gallium oxide, Ga2O3, from pure elements was derived. Using values of the measured e.m.f. for the cell with xGa = 1.0, the following temperature dependence was obtained: ΔfGm,Ga2O3∘(±4kJ·mol-1J)=-1061.7235+0.2899T/K.Next, the activity of the gallium was derived as a function of the alloy composition from the values of the measured e.m.f. Activities of silver were calculated using the Gibbs–Duhem equation.The drop calorimetric measurements were carried out at two temperatures, viz. 923 K and 1123 K, using a Setaram MHTC calorimeter. Integral enthalpies of mixing of liquid binary alloys were determined at those temperatures. Finally, thermodynamic properties of the liquid alloys were described with the Redlich–Kister equation using ThermoCalc software.