Physicochemical properties of liquid Ag–Bi–Sn

Free energies of mixing in liquid Ag–Bi–Sn are deduced from EMF measurements. The excess free energy was found to adopt negative values near the Ag-rich corner, whereas positive values are the dominant feature towards the Bi–Sn side of the ternary system. The section with the constant atomic fraction ratio of cAg/cBi=2cAg/cBi=2 marks the tentative borderline between the two regimes.The surface tension and the surface concentrations of the liquid system were calculated with the help of the experimental thermodynamic activity coefficients. The results indicate a preferential segregation of Bi and Sn atoms into the surface layer. Excepting the Ag-rich corner of the system (cAg>0.9), the surface is only scarcely populated by Ag atoms. Up to composition ratios of cAg/cBi≈2 the surface concentration of Ag is found to be less than 1 at%. As a consequence, over a wide range of the ternary system, the surface tension is not very different from the value of pure Bi or Sn.The calculated viscosity is indicated to be primarily dependent on the concentration of Ag, whereas the substitution of Bi by Sn at a constant concentration of Ag yields only small changes. Due to their close correlation with the free energy of mixing, the viscosities show positive deviations from ideality for alloys with cAg/cBi<2 and negative deviations if cAg/cBi>2.