Study of the Ni_(3+-x)S_2 phase in the Ni-S system with emphasis on the phases of high-form Ni_3S_2(#beta#_1), and Ni_4S_3(#beta#_2)

摘要

The phase Ni_(3+-x)S_2 in the Ni-S system is studied by means of high-temperature X-ray powder diffraction and differential thermal analysis. It is divided to two unquenchable #beta#_1 and #beta#_2 phases which we limited solid solutions, and there is an immiscible field between them. The #beta#_1 phase has a face centered cubic cell and is only stable at temperatures from 533 +- 3 to 800 +- 3 deg C. With a composition of Ni_3S_2 it inverts into low-form (heazlewoodite) at 565 +- 3 deg C. Its transition is reversible. Whereas, the #beta#_2 phase has a primitive cubic cell and is stable at temperatures above 524 +- 3 deg C. It breaks down to a mixture of heazlewoodite and high-form god-levskite at this temperature. Also it melts incongruently to high-form millerite and liquid at 806 +- 3 deg C.