Abstract
High pressure and temperature behavior of stoichiometric FeS (troilite) was studied up to 16GPa and 800°C, and the phase diagram of FeS was determined. There were found four stable phases; the troilite phase, the hexagonal phase, the NiAs type phase and the high pressure phase with a monoclinic cell. Some remarkable phenomena were also observed in the stable region of the hexagonal phase near the phase transition to the monoclinic phase; convergence of iso c/a curves to the boundary, an inflection in the compression curve at 300°C, and a very small coefficient of cubical expansion. These results suggested an electronic transition of the hexagonal phase between 6 and 8GPa. The transition could explain an anomaly in the boundary between the hexagonal phase and the monoclinic high pressure phase.
