Thermodynamic Investigation of the Ni-rich side of the Ni-P system

Ni(P) is used in electronics as a protective layer during the soldering process. New thermodynamic information on Ni-P alloys has been obtained in the Ni-rich part (up to the molar fraction xP = 0.40) by using a high-temperature direct drop calorimeter. The experimental trend of ΔfH° [kJ· (mol of atoms)-1] of the Ni-P alloys versus composition (xP) has been plotted and the following standard enthalpy of formation [ΔfH° ± 2 kJ· (mol of atoms)-1] values interpolated for the Ni-rich phases: -48.0 (Ni3P), -55.0 (Ni5P2), -56.0 (Ni 12P5), and -61.0 (NiP2). Our results have been compared with those reported in the literature and discussed