Thermodynamische Untersuchung der Systeme Gallium-Blei und Gallium-Thallium

Abstract

To find the thermodynamic properties of the GaTl and GaPb systems the enthalpies of mixing of the liquid alloys of the entire concentration range were measured using a high-temperature calorimeter, and the entropies of mixing were determined based on the results by an evaluation of the solubility equilibria. Corresponding to the strong tendency to decomposition of these alloys the enthalpies of mixing are positive and of relatively high magnitude (in the GaTl system ΔH max = 880 and in the GaPb system ΔH max = 920 cal/g-atom). Also, the excess entropies are positive as expected; however the values are small (in the GaTl system ΔS ex max = 0.05 and in the GaPb system ΔS ex max = 0.06 cal/g-atom °K). It could be shown that for alloys of gallium with elements of the 6th period of the Periodic Table (Group III to V), in addition to the misfit enthalpy caused by differences in atomic radii, still another contribution, apparently caused by electronic peculiarities, is contained in the enthalpy of mixing. In alloys of gallium with elements which are found in the same or in a neighbouring period such a contribution seems to be insignificant.