Thermodynamic assessment of the Bi–Rb binary system

Abstract

The thermodynamic assessment of the Bi–Rb system was carried out by using the CALculation of PHAse Diagrams (CALPHAD) method on the basis of experimental thermodynamic data and phase equilibrium measurements. Considering the short range ordering behavior of the liquid phase, the associate model was used with the constituent species Bi, BiRb, BiRb3 and Rb. All the intermetallic compounds, Bi2Rb, Bi2Rb3, Bi4Rb5, α-BiRb3 and β-BiRb3, with no experimentally determined solubility ranges were treated as stoichiometric compounds. The solution phases, the Bi-rich terminal phase Rhombohedral_A7 and the Rb-rich terminal phase BCC_A2, were treated as the pure substances since the extremely small solubility of the second alloying element in each of these phases. A set of self-consistent thermodynamic parameters was obtained for the Bi–Rb system and the CALPHAD results can reproduce the experimental thermochemical properties and the measured phase equilibrium relations well.