Untersuchung der thermodynamischen Eigenschaften flüssiger gallium-zinn- und gallium-wismut-Legierungen

Abstract

For the determination of the thermodynamic characteristics of liquid Ga-Sn and Ga-Bi alloys the integral enthalpies of mixing were measured directly with a high-temperature calorimeter and the other excess functions calculated from melting equilibria using the measured values. The enthalpies of mixing are positive in both systems. The maximum values are ΔH max = 234 cal/g-atom and ΔH max = 504 cal/g-atom for the systems Ga-Sn and Ga-Bi, respectively. The excess entropies of liquid Ga-Sn alloys are positive ( ΔS ex max = +0.25 cal/g-atom °K), while in the intermediate concentration region of the system Ga-Bi negative ΔS ex values were found ( ΔS ex max = −0.2 cal/g-atom °K). A discussion of the factors which determine the thermodynamic behavior of an alloy leads to the assumption that the enthalpies of mixing in both systems are essentially dependent on an atomic misfit in the melt as the result of differences in atomic volumes.