PROPERTIES OF NI3S2 AT HIGH-TEMPERATURES

The structural properties of the two modifiCations of Ni3S2 are report ed. In alpha-Ni3S2 at low temperature the Ni atoms occupy tetrahedral sites, and any homogeneity range is very limited up to the transformat ion into beta-Ni3S2 at 838 +/- 5 K. Unit-cell data are provided for th e extremely defect, ionic-conducting beta-Ni3S2 phase as a function of composition and temperature. Thermal expansion data are presented for both modifications. The structure of beta-Ni3S2 is considered in rela tion to other fast-ionic conductors with a face-centered cubic sublatt ice of anions.