MIXING ENTHALPIES OF Sr–Sb MELTS

Abstract

The mixing enthalpies of Sr–Sb melts were measured by isoperibolic calorimetry at 1230 K over the entire composition range referred to the liquid components. Extremely large exothermic mixing effects were found ( = –70.1 ± 4.8 kJ/mole), indicating very strong interaction between the components connected with short-range ordering in melts. The mixing enthalpies agree with the Sr–Sb phase diagram. In this system, a series of intermetallic compounds SrSb, SrSb₃, Sr₃Sb₂, and Sr₂Sb was found. Minimum for the liquid alloys corresponds to the composition range where SrSb and Sr₃Sb₂ phases exist. The mixing enthalpies were found to be less exothermic than those for the intermetallic phases. This agrees with data for the alloys in systems with strong interaction between components and is indicative of short-range ordering in liquid state. The mixing enthalpies for Mg (Ca, Sr)–Sb melts decrease in the Mg–Sb → Ca–Sb → Sr–Sb series, which agrees with increasing differences in electronegativity of the alloys com-ponents.