Thermodynamic reassessment of Ni–Ga binary system

Abstract

New experimental measurements of the phase diagram and the mixing enthalpy of liquid phase along with the previous experimental data were used in a reassessment of the Ni–Ga system. A set of self-consistent thermodynamic parameters of the Ni–Ga system is obtained using the calculation of phase diagram (CALPHAD) technique, and the available phase diagram and thermodynamic data are reproduced well within experimental error limits. Some noticeable improvements are obtained in the present work compared with the previous assessment: (1) the calculated Ga-rich liquidus is more reasonable; (2) Ni3Ga7 is adopted as the most Ga-rich compound rather than NiGa4; (3) the Ni5Ga3 phase is treated as the nonstoichiometric compound with consideration of its narrow homogeneity range; (4) the phase transformation between B81.5_Ni3Ga2 and Ni13Ga9 is considered instead of treating them as Ni3Ga2 phase simply; (5) the latest experimental data of mixing enthalpy for the liquid phase are adopted. The present study can be used as a basis for the development of a thermodynamic database of the Ni-based semiconductor alloy systems.