Syntheses and crystal structures of three barium uranium sulfides

The barium uranium sulfides Ba3.69US6, BaUS3, and BaU2S5 have been synthesized at 1273, 1323, and 1323 K, respectively. The structures of these compounds have been determined by single-crystal X-ray diffraction methods. They crystallize in space groups D3d6−R3¯c, D2h16−Pnma, and C2h5−P21/c, respectively. Among these three ternaries and Ba2US6 the coordination geometries about the U atoms vary considerably. Ba3.69US6 is a mixed U4+/U5+compound whereas the others are U4+ compounds. The decreasing dimensionality of the four compounds with increasing Ba–to–U content shows the expected trend.

View of the structure of Ba3.69US6 down [1 0 1].Figure optionsDownload as PowerPoint slideHighlights
► The barium uranium sulfides Ba3.69US6,BaUS3, and BaU2S5 have been synthesized and characterized.
► Ba3.69US6 is a new mixed valent U4+/U5+ compound.
► Dimensionality of these compounds decreases with increasing Ba–to–U content.