The U5+ compound Ba9Ag10U4S24: Synthesis, structure, and electronic properties

Abstract : Black crystals of Ba9Ag10U4S24 have been made by direct combination of BaS, Ag, U, and S at 1273 K. This compound crystallizes in a new structure type in the space group C-4v(10)-I4cm of the tetragonal system with four formula units in a cell with lattice constants a=13.9189(6) angstrom and c=23.7641(11) angstrom (V=4604(5) angstrom(3)). Multiphoton Luminescence Spectroscopy measurements are consistent with the noncentrosymmetric nature of the structure. In the structure each U atom is octahedrally coordinated by six S atoms, whereas three of the five crystallographically independent Ag atoms are tetrahedrally coordinated to four S atoms, another has a seesaw coordination to four S atoms, and the last has a triangular coordination to three S atoms. The overall structure consists of the three-dimensional stacking of the US6, AgS4, and AgS3 polyhedra to leave channels in which Ba atoms reside. Based on the values of the U-S interatomic distances, the compound Ba9Ag10U4S24 contains U5+ and charge balance is achieved with the formal oxidation states of 9 Ba2+, 10 Ag1+, 4 U5+ and 24 S2-. DFT calculations predict an antiferromagnetic ground state and a band gap of 2.1 eV. Resistivity measurements indicate that the compound is a semiconductor with a complex activation mechanism and activation energies ranging from 0.03(1) eV to 0.08(1) eV.
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Journal of Solid State Chemistry, Elsevier, 2015, 221, pp.398-404. 〈10.1016/j.jssc.2014.10.014〉
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Soumis le : vendredi 12 mai 2017 - 14:43:56
Dernière modification le : jeudi 1 février 2018 - 01:42:06

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Adel Mesbah, Wojciech Stojko, Sébastien Lebègue, Christos D. Malliakas, Laszlo Frazer, et al.. The U5+ compound Ba9Ag10U4S24: Synthesis, structure, and electronic properties. Journal of Solid State Chemistry, Elsevier, 2015, 221, pp.398-404. 〈10.1016/j.jssc.2014.10.014〉. 〈hal-01521898〉

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