Thermochemistry of the nickel–phosphorus system

In the first part, an extensive overview is given over the thermodynamic information for the nickel–phosphorus system which is available in the literature. In the second part, phosphorus vapor pressure measurements over nickel–phosphorus alloys are described for which an isopiestic method was employed. Data points were obtained between 33.82 and 44.40 at% P in the temperature interval from 977 to 1325 K. Based on these measurements partial thermodynamic properties and integral Gibbs energy values were determined. The standard molar Gibbs energy of formation of Ni5P4 for the temperature range 977–1042 K was obtained as: Δ f G m o ( Ni 5 P 4 ) ( s ) ± 9.8 / ( kJ mol − 1 ) = − 632.1 + 0.2136 T / K