Enthalpy of mixing of liquid Li-Sb-Sn alloys

Abstract

The partial and integral molar enthalpies of mixing of liquid Li-Sb-Sn alloys were determined by drop calorimetry at 879 K along ten sections xLi:xSb ≈ 2:3, xLi:xSb ≈ 3:7, xLi:xSn ≈ 1:1, xLi:xSn ≈ 3:5, xLi:xSn ≈ 1:3, xSb:xSn ≈ 4:1, xSb:xSn ≈ 13:7, xSb:xSn ≈ 1:1, xSb:xSn ≈ 1:3 and xSb:xSn ≈ 3:17. A check of enthalpy values at the crossing points of the ten sections proved high accuracy of the measurements. The behavior of the partial and integral enthalpy of mixing along these sections can be grouped into three types, depending on the starting binary systems. For the description of the integral enthalpy over the entire concentration range our experimental 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 models of Muggianu and Toop is given. The entire system shows a strong exothermic behavior with a minimum of ΔmixH ≈ −65,000 J mol−1 in the binary LiSb near to Li3Sb. From experimental ternary data the phase boundary of the liquid at 879 K was derived. It showed that high melting Li3Sb dominates the solidification behavior of the Li-Sb-Sn system.