Bismuth activity measurements and thermodynamic re-optimization of the Ni–Bi System

Abstract

Bismuth thermodynamic activities in Ni – Bi liquid solutions have been measured by the modified isothermal isopiestic method at 1723, 1753 and 1773 K. These results are coupled with thermochemical and topological data from literature, in order to achieve reliable re-optimization of the Ni – Bi system by the CALPHAD method. The model of disordered substitutional solutions has been applied to the liquid phase and to the face-centered cubic solid solutions (Ni). The compound NiBi3 is stoichiometric and is modeled by a two-sublattice model corresponding to its formula. The nickel solubility in the solid bismuth is negligible, which is why the phase (Bi) is considered as consisting of bismuth only. The description Bi: Ni, Va has been used for the thermodynamic modeling of the nonstoichiometric NiBi phase.

Notes on some supposed transitions of the phase NiBi

“…% Bi. Nevertheless, Vassilev et al [9] suggested that the magnetic effects were due to the presence of the face centered cubic phase (FCC-Ni) in the samples. This hypothesis was supported by the information that the transition temperature estimated by Yoshida et al [12] (640 K) is close to that of the Curie point of the pure Ni (633 K).…”

“…Vassilev et al [9,11] have recently done experimental studies and thermodynamic optimization of this system. During those studies ambiguous information about some properties (magnetism [12], heat capacity [13]) of the phase NiBi was found in the literature.…”

“…The superconductivity of Ni-Bi phases was also of interest [3 -6]. The system Ni-Bi is important in the prospect of lead-free solders development [7][8][9] and is included in the Thermodynamic database created in the frames of the European concerted action for development of lead-free solders COST 531 [10].…”

Wet‐chemical synthesis and characterization of NiBi nano‐ and micro‐particles

“…In this aspect, experimental studies and thermodynamic optimization of this system have recently been done by Vassilev et al [6,10,11]. Moreover, Teyeb et al [12] synthesized NiBi nanosized particles using organic precursors but these are relatively expensive compared to the inorganic reagents.…”

“…The other component (Bi) of the studied materials is an important ingredient of many prospective lead-free microelectronic solders [4][5][6]. Moreover, nickel-bismuth alloys are applied to control the silicon steels kinetics of galvanizing [7] and are sought as bismuth suppliers in order to substitute lead in freemachining steels [8].…”