Combined Thermodynamic Description and Experimental Investigation of the Ternary Ag–Bi–Ge System

Abstract

In this study, the phase diagram of the ternary Ag–Bi–Ge system was thermodynamically assessed and experimentally investigated, which to our knowledge has not been previously done. Differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and X-ray powder diffraction (XRD) were applied in order to experimentally assess three vertical sections and two isothermal sections at 200 °C and 400 °C of the Ag–Bi–Ge system. Results of the SEM–EDS and XRD analysis revealed existence of (Ge), (Ag) and (Bi) solid solution phases and absence of any ternary phases. Crystal structures of the identified phases and their corresponding lattice parameters were determined by XRD technique. Phase transition temperatures, including liquidus, solidus and temperature of an invariant reaction, were determined by means of DTA. Thermodynamic calculation of the Ag–Bi–Ge ternary phase diagram was carried out on the basis of optimized thermodynamic parameters for the constitutive binary systems acquired from the literature. Calculated liquidus projection of the Ag–Bi–Ge system and the determined invariant reactions are presented in the study as well. A close mutual agreement between the experimental results and the calculated phase equilibria was obtained.