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 x P = 0.40) by using a high-temperature direct drop calorimeter. The experimental trend of Δ f H ° [kJ·(mol of atoms) −1 ] of the Ni−P alloys versus composition ( x P ) has been plotted and the following standard enthalpy of formation [Δ f H ° ± 2 kJ·(mol of atoms) −1 ] values interpolated for the Ni-rich phases: −48.0 (Ni 3 P), −55.0 (Ni 5 P 2 ), −56.0 (Ni 12 P 5 ), and −61.0 (NiP 2 ). Our results have been compared with those reported in the literature and discussed.