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

Abstract

a b s t r a c tBlack crystals of Ba 9 Ag 10 U 4 S 24 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 10 4v À I4cm of the tetragonal system with four formula units in a cell with lattice constants a¼13.9189(6) Å and c¼23.7641(11) Å (V¼4604(5) Å 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 US 6 , AgS 4 , and AgS 3 polyhedra to leave channels in which Ba atoms reside. Based on the values of the U-S interatomic distances, the compound Ba 9 Ag 10 U 4 S 24 contains U 5 þ and charge balance is achieved with the formal oxidation states of 9 Ba 2 þ , 10 Ag 1 þ , 4 U 5 þ and 24 S 2À . 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.

Revealing the oxidation number and local coordination of uranium in Nd 2 Zr 2 O 7 pyrochlore: A photoluminescence study

“…The spectrum exhibited two emission signals at 415-475 nm which was ascribed to metastable uranyl (V), whereas the emission signal between 480 and 560 nm was identified as uranyl (VI). Recently luminescence properties of U(5 þ) was also investigated in Ba 9 Ag 10 U 4 S 24 [25]. The fact that a broad spectrum is observed in this case rules out the possibility of uranium being present in þ3, þ 4 and þ 5.…”

Synthesis, crystal structure, resistivity, and electronic structure of the U(V) quaternary polyselenide Ba8PdU2Se12(Se2)2

“…However, there are a very few compounds of U 3 þ or U 5 þ . Examples of U 3 þ compounds include ScUS 3 [24] and ScU 3 S 6 [25]; examples of U 5 þ compounds include Tl 3 Cu 4 USe 6 [15], Ba 9 Ag 10 U 4 S 24 [26], Ba 3 AgUS 6 [27], and K 2 Cu 3 US 5 [28] were performed in sealed 6 mm carbon-coated fused-silica tubes. Depleted U powder was obtained by hydridization and decomposition of uranium turnings (IBI Labs) in a modification [29] of a previous literature method [30].…”

Syntheses, crystal structures, and electronic properties of Ba 8 Si 2 US 14 and Ba 8 SiFeUS 14

“…Among these compounds, the actinide (An) chalcogenides have also been extensively studied because of the interesting properties of the f orbitals and their potential interaction with d elements in multinary M/AnQ. Among these, we can cite: AMAnQ 3 (A ¼ alkali metal) [6e8], A 6 Cu 12 U 2 S 15 [9], Tl 3 Cu 4 USe 6 [10], KCuThS 3 , K 2 Cu 2 ThS 4 , K 3 Cu 3 Th 2 S 7 [11], K 2 Cu 3 US 5 [12], CsTiUTe 5 [13], Ba 2 Cu 2 AnS 5 [14,15], Ba 9 Ag 10 U 4 S 24 [16], Ba 3 MUS 6 (M ¼ Ba, Fe, Ag) [17], Ba 4 Cr 2 US 9 [18], and Ba 3 Hg 3 U 3 S 18 [19]. These compounds are mainly obtained through solid-state reactions using flux methods [20] or by direct combination of elements.…”