Thermodynamic properties of liquid Au-Cu-Sn alloys determined from electromotive force measurements

Highlights: → A full thermodynamic description of the liquid ternary Au-Cu-Sn system is reported. → The electromotive force method with a liquid electrolyte was used to determine the activity of tin in the alloys. → The partial free energies of tin in this system were calculated from the obtained EMF values. → The Gibbs-Duhem integration was used to calculate the integral Gibbs free energy and integral enthalpy of the entire system. - Abstract: The thermodynamic properties of the ternary Au-Cu-Sn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Three different cross-sections with constant Au:Cu ratios of 3:1, 1:1, and 1:3 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 1023 K. The partial free energies of Sn in liquid Au-Cu-Sn alloys were obtained from EMF data. The integral Gibbs free energy and the integral enthalpy at 900 K were calculated by Gibbs-Duhem integration. The ternary interaction parameters were evaluated using the Redlich-Kister-Muggianu polynomial.