Concentration fluctuations and surface tension in liquid Au-Sn-Zn

Experimental thermodynamic data were applied to calculate the surface tension and the long-wavelength limit of the concentration-concentration fluctuations S_cc(0) in the ternary system Au-Sn-Zn. The fluctuations in the concentration of Zn and in particular those of Sn show marked maxima around Au₁₅Sn₃₀Zn₅₅ whereas for Au the fluctuations are smaller than those of a non-interacting ideal mixture. Over an extremely wide range of compositions the surface layer of the ternary is found to be primarily populated by Sn atoms. Excepting the alloys with larger amounts of Au (c_Au > 0.3) or high contents of Zn (c_Zn > 0.7) the surface tension is not very different from that of pure by Sn (0.52–0.60 Nm⁻¹). The progressive substitution of Sn by Zn at a constant value of c_Au≈ 0.3 leaves the surface tension practically constant up to c_Zn≈ 0.5. In sections of constant c_Au/c_Sn with c_Au/c_Sn > 0.3 the surface tension is observed to even pass through pronounced minima if larger amounts of Zn are added.