URANIUM CHALCOGENIDES .I. STRUCTURAL AND MAGNETIC PROPERTIES OF SULPHIDES AND SELENIDES IN RANGE UX1.5 TO UX3

X-ray studies of uranium sulphides have confirmed the existence of the U3S5- and US3-phases and have shown that US2α and US2β are phases with different compositions. US2α with tetragonal structure has a range of homogeneity between about US1·80 and US1·93 after heat treatment up to 1300°C. Samples with composition US1·95 and US1·98 contain a mixture of US2α and US2β, while US2·00 consists of only US2β with orthorhombic structure and has no appreciable range of homogeneity. The uranium-richest selenide prepared by heating the elements at 1000°C was the U3Se5-phase. At higher selenium contents, the phase USe2α was observed but not the USe2β- or USe2γ-phases. USe2α has a range of homogeneity between USe1·85 and USe2·0 and is isostructural with US2α. Magnetic susceptibility measurements in the range -185 to 445°C on samples with compositions US1·6, US1·9, US2·0, US3·0, USe2·0, and USe3·0 indicate the presence of two unpaired 5f electrons in all the samples. © 1968.