Electromotive force study of the liquid silver-bismuth-tin alloys

Abstract

The Ag−Bi−Sn alloy system has been assessed twice, so far, for its potential applications as a lead-free solder material. The first assessment was based on binary data only; the second assessment introduced ternary parameters. It was noted in conclusion that more experimental studies were needed, especially for the liquid phase. The electromotive force (emf) measurement method was used in this study to determine the thermodynamic properties of liquid Ag−Bi−Sn alloys using solid electrolyte galvanic cells as shown below: Re, Ag−Bi−Sn, SnO2 |Yttria Stabilized Zirconia| Ni, NiO, Pt, Re, Sn, SnO2 |Yttria Stabilized Zirconia| Ni, NiO, Pt. Alloy compositions for in vestigation were chosen along three constant Bi-to-Sn ratio lines (1/3, 1, and 3) and with the silver content changing from 10 up to 90 at.%, every 10 at.%, resulting in a total of 27 different alloy samples. The temperature of the measurements varied from 975 to 1400 K. A linear dependence of the emf on temperature was observed for all compositions, and the appropriate line equations were derived. Excess partial Gibbs energies of Sn were then calculated at 1200 K and compared with the results of the calculations of both assessments; Gibbs energy of formation of SnO2 was determined as well. It was then shown that our new emf data fit better to the binary formalism-based calculations than to the second assessment results.