Thermodynamic and surface properties of liquid Bi-Ga-Sn alloys

The results of investigation of thermodynamics and surface properties of liquid Bi-Ga-Sn alloys are presented. A comparative analysis between thermodynamic data obtained experimentally - using Oelsen calorimetry and EMF measurements, and those obtained theoretically, i.e. using different thermodynamic predicting models have been done. Positive values of the integral molar enthalpies of mixing in liquid state in the case of all binary subsystems are in accordance with the corresponding activity values for constituent components, characterized by positive deviation from ideal behavior at all considered temperatures. An attempt has been made to link surface phenomena of ternary Bi-Ga-Sn system and its binary Bi-Ga, Bi-Sn and Ga-Sn subsystems with the bulk through the study of the concentration dependence of various thermodynamic, structural and surface properties in the frame of statistical mechanical theory in conjunction with the quasi-lattice theory (QLT). This formalism provides valuable qualitative insight into mixing processes that occur in molten alloys. Thermodynamic data together with surface tension data of pure components are used as an input for the calculation of surface tension, surface composition as well as the microscopic functions of molten alloy systems mentioned above. The calculation is based on Butler's equation that assumes an outermost monolayer as a surface. Each of parameters involved in the surface functions is correlated to the corresponding value of the bulk in terms of a surface reduced coordination. The results obtained support a demixing tendency in all analysed liquid alloy systems.