Synthesis and characterization of the new uranium yttrium oxysulfide UY4O3S5

Red needles of UY{sub 4}O{sub 3}S{sub 5} have been synthesized by the solid-state reaction at 1273 K of UOS and Y{sub 2}S{sub 3} with Sb{sub 2}S{sub 3} as a flux. UY{sub 4}O{sub 3}S{sub 5} adopts a three-dimensional structure that contains five crystallographically unique heavy-atom positions. U and Y atoms disorder on one eight-coordinate metal position bonded to four O atoms and four S atoms and two seven-coordinate metal positions bonded to three O atoms and four S atoms. Another eight-coordinate metal position with two O and six S atoms and one six-coordinate metal position with six S atoms are exclusively occupied by Y atoms. UY{sub 4}O{sub 3}S{sub 5} is a modified Curie-Weiss paramagnet between 1.8 and 300 K. Its effective magnetic moment is estimated to be 3.3(2) mu{sub B}. UY{sub 4}O{sub 3}S{sub 5} has a band gap of 1.95 eV. The electrical resistivity along the [010] direction of a single crystal shows Arrhenius-type thermal activation with an activation energy of 0.2 eV. - Graphical abstract: View of the crystal structure of UY4O3S5.