Study of the Ni3 +/- xS2 phase in the Ni-S system with emphasis on the phases of high-form Ni3S2(beta(1)), and Ni4S3(beta(2))

The phase Ni3+/-xS2 in the Ni-S system is studied by means of high-temperat ure X-ray powder diffraction and differential thermal analysis. It is divid ed to two unquenchable beta (1) and beta (2) phases which are limited solid solutions, and there is an immiscible field between them. The beta (1) pha se has a face centered cubic cell and is only stable at temperatures from 5 33 +/- 3 to 800 +/- 3 degreesC. With a composition of Ni3S2 it inverts into low-form (heazlewoodite) at 565 +/- 3 degreesC. Its transition is reversib le. Whereas, the beta (2) phase has a primitive cubic cell and is stable at temperatures above 524 +/- 3 degreesC. It breaks down to a mixture of heaz lewoodite and high-form godlevskite at this temperature. Also it melts inco ngruently to high-form millerite and liquid at 806 +/- 3 degreesC.