Calorimetric studies of Cu-Li, Li-Sn, and Cu-Li-Sn

Integral molar enthalpies of mixing were determined by drop calorimetry for Cu-Li-Sn at 1073 K along five sections x_Cu/x_Sn ≈ 1:1, x_Cu/x_Sn ≈ 2:3, x_Cu/x_Sn ≈ 1:4, x_Li/x_Sn ≈ 1:1, and x_Li/x_Sn ≈ 1:4. The integral and partial molar mixing enthalpies of Cu-Li and Li-Sn were measured at the same temperature, for Li-Sn in addition at 773 K. All binary data could be described by Redlich-Kister-polynomials. Cu-Li shows an endothermic mixing effect with a maximum in the integral molar mixing enthalpy of ∼5300 J · mol^-1 at x_Cu = 0.5, Li-Sn an exothermic minimum of ∼ -37,000 J · mol^-1 at x_Sn ∼ 0.2. For Li-Sn no significant temperature dependence between 773 K and 1073 K could be deduced. Our measured ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. Additionally, a comparison of these results to the extrapolation model of Chou is given.