Thermodynamic Study and Re-optimization of the Au-Ga Binary System

Abstract

Activities of gallium in the liquid Au-Ga alloys were determined using galvanic cells with the solid oxide electrolyte. The cells of the type:were used in the temperature range from 1050 to 1273 K, and for four alloy compositions x Ga = 0.2, 0.4, 0.6 and 0.8. From the measured e.m.f.'s the activity of gallium was derived, which taken together with the recently measured heat of mixing provided precise description of the thermodynamic properties of the liquid phase. This study was supplemented with DTA experiments which were performed for three alloy compositions, namely 0.15, 0.25 and 0.40 gallium mole fraction. The results of these experiments verified with temperature of respective invariant reactions. Finally, present results, taken together with the information existing in the literature, were used for the calculation of the optimized Au-Ga phase diagram. ThermoCalc software was applied to complete these calculations.

DTA measurements in the ternary Ag-Au-Ga system

“…The gas atmosphere was pure argon of minimum mass fraction (99.9999 mass%) obtained from Air Products. DTA measurements were carried out on Ag-Au-Ga alloys along two cross-sections, with X Ag /X Ga = 1:1 and X Au /X Ga = 1:1, and in the temperature range from 473 K to 1300 K. The experimental procedure of DTA measurements is the same as in the case of Au-Ga system [28], Ag-In-Sb system [31], and Ag-Cu-Ga system [32]. The samples of the alloys were prepared from pieces of pure silver, gold, and gallium metals.…”

“…Thermodynamic properties and phase equilibrium data for three binary systems Ag-Au [27], Au-Ga [28] and Ag-Ga [29,30] have been studied and can be found in the literature. They are described in details in the previous work [26].…”

“…The prediction of ternary Ag-Au-Ga diagram by applying the CALPHAD method was done by using Pandat 2017 software [33] and is compared with the experimental data obtained in this work. At first, this prediction was based on the existing information about the assessed binary systems: Ag-Au [27], Au-Ga [28], and Ag-Ga [30]. The binary thermodynamic parameters used for the prediction of phase equilibria in the ternary Ag-Au-Ga system were taken from the previous work [26].…”

Phase equilibria in the ternary Ag-Au-Ga system: Isothermal sections at 250°C and 450°C

“…The phases bAu 7 Ga 2 , b'Au 7 Ga 2 , gAu 7 Ga 3 were described as intermetallic compounds which are treated as stoichiometric compounds (Au a Ga b ) because of their narrow homogeneity ranges determined by Cooke and Hume-Rothery [29,34]. Recently re-optimization of the Au-Ga system was carried out by Jendrzejczyk-Handzlik [35]. In this…”

“…Prediction of ternary Ag-Au-Ga system, which was done by using Pandat 8.1 software [36] is compared with experimental data obtained in this work. This prediction is based on information from assessments of binary systems: Ag-Au [21], Ag-Ga [26] and Au-Ga [35]. The binary thermodynamic parameters used for the prediction of phase equilibria in the ternary Ag-Au-Ga system are listed in Table 3.…”