We present experimental results on melting and subsolidus phase relations in the Ni–Ni2P system at 6 GPa and 900–1600°C. The system has four stable phosphides: Ni3P nickelphosphide, Ni8P3/Ni5P2, Ni12P5 and Ni2P transjordanite. The Ni12P5 phase becomes unstable at 900°C and decomposes into Ni5P2 and Ni2P. The eutectic Ni–Ni3P locates at 950°C and 20 mol% P. Ni3P melts incongruently at 1075°C to Ni5P2 and liquid containing 23 mol% P. Ni8P3 and Ni5P2 form a homogeneity range with crystal structure close to Ni5P2. The Ni5P2–Ni2P eutectic locates at 1175°C and 29 mol%. Ni2P melts congruently at 1250°C. The quenched products of nickelphosphide liquid correspond to the eutectics composition and can serve as indicators for reconstructing the P–T–X conditions recorded in meteoritic and terrestrial Fe–Ni–P assemblages. The Ni–P stoichiometries, which were not observed in the equilibrium phase diagrams, including Ni4P and Ni5P, remain enigmatic.
ASJC Scopus subject areas