CrSe2, a new layered dichalcogenide

Abstract CrSe2 was prepared by oxidation of KCrSe2 with I2 in acetonitrile at ambient temperature. It has the Cd(OH)2 structure with a = 3.399, c = 5.915 A at 300 K; the compound is metastable and transforms into Cr2Se3 and Se around 600 K. Between ≈ 180 and ≈ 160 K a (reversible) phase transition occurs with an abrupt decrease of ≈ 1% of the c-axis and the appearance of some weak reflections. This paper reports the first physical properties obtained on powders and compacts by X-ray diffraction, thermal analysis, transport (resistivity, Hall effect, thermoelectric power) and magnetic susceptibility measurements. These data, especially the lattice parameters, show a remarkable behaviour with temperature and suggest that CrSe2 has itinerant d electrons.