12138-21-5Relevant articles and documents
Synthesis, structure, and optical properties of CsU2(PO 4)3
Oh, George N.,Ringe, Emilie,Van Duyne, Richard P.,Ibers, James A.
, p. 124 - 129 (2012)
CsU2(PO4)3 was synthesized in highest yield by the reaction in a fused-silica tube of U, P, and Se in a CsCl flux at 1273 K. It crystallizes with four formula units in space group P21/n of the monoclinic system in a new structure type. The structure of CsU 2(PO4)3 is composed of U and Cs atoms coordinated by PO43- units in distorted octahedral arrangements. Each U atom corner shares with six PO43- units. Each Cs atom face shares with one, edge shares with two, and corner shares with three PO43- units. The structure shares some features with the sodium zirconium phosphate structure type. X-ray powder diffraction results demonstrate that the present CsU2(PO 4)3 compound crystallizes in a structure different from the previously reported β′- and γ-CsU2(PO 4)3 compounds. CsU2(PO4)3 is highly pleochroic, as demonstrated by single-crystal optical absorption measurements.
Synthesis, structure, and electrical resistivity of Cs3U 18Se38
Oh, George N.,Ibers, James A.
, p. 81 - 86 (2012)
Cs3U18Se38 was synthesized by the solid-state reactions of U, Se, CsCl or Cs2Se3, and P or As at 1273 K. This compound crystallizes in a new structure in the tetragonal space group D184h-I4/mcm. The asymmetric unit contains U atoms in four different coordination environments. The overall three-dimensional network structure contains channels along the c axis, in which the Cs atoms lie. The formula Cs3U18Se38 does not charge balance with the typical formal oxidation states of the elements. Electrical resistivity measurements conducted on a single crystal reveal a broad feature at 225 K, atypical semiconductor behavior below 57 K, and a calculated band gap of 0.0030(1) eV.
Crystal structure and magnetic properties of the hexagonal uranium dichalcogenides γUS2 and γUSe2
Daoudi,Levet,Potel,Noel
, p. 1213 - 1218 (1996)
The crystal structure of the hexagonal uranium disulfide γUS2 (hexagonal P62m, a = 7.236(2) A, c = 4.062(1) A, γ = 120°) has been determined from single crystal X-ray diffraction data and confirmed by Rietveld refinements from X-ray powder diffraction intensities of the isostructural selenide γUSe2 (a = 7.6328(3) A, c = 4.1897(2) A, γ = 120°). They crystallize with the anti-Fe2P-type structure. The sulfide γUS2 exhibits weak ferromagnetism below ≈10 K, and the selenide is a ferromagnet with a Curie temperature of ≈20 K and an ordered moment of 0.72 μB/U under 20 kGauss.
Facile Oxide to Chalcogenide Conversion for Actinides Using the Boron-Chalcogen Mixture Method
Breton, Logan S.,Klepov, Vladislav V.,Zur Loye, Hans-Conrad
, p. 14365 - 14373 (2020)
Actinide chalcogenides are of interest for fundamental studies of the behavior of 5f electrons in actinides located in a soft ligand coordination environment. As actinides exhibit an extremely high affinity for oxygen, the synthesis of phase-pure actinide chalcogenide materials free of oxide impurities is a great challenge and, moreover, requires the availability and use of oxygen-free starting materials. Herein, we report a new method, the boron-chalcogen mixture (BCM) method, for the synthesis of phase-pure uranium chalcogenides based on the use of a boron-chalcogen mixture, where boron functions as an oxygen sponge to remove oxygen from an oxide precursor and where the elemental chalcogen effects transformation of the oxide precursor into an oxygen-free chalcogenide reagent. The boron oxide can be separated from the reaction mixture that is left to react to form the desired chalcogenide product. Several syntheses are presented that demonstrate the broad functionality of the technique, and thermodynamic calculations that show the underlying driving force are discussed. Specifically, three classes of chalcogenides that include both new (rare earth uranium sulfides and alkali-Thorium thiophosphates) and previously reported compounds were prepared to validate the approach: binary uranium and thorium sulfides, oxide to sulfide transformation in solid-state reactions, and in situ generation of actinide chalcogenides in flux crystal growth reactions.
La2USe3S2: A Serendipitously Grown Lanthanide/Actinide Chalcogenide from a Eutectic Halide Flux
Usman, Mohammad,Morrison, Gregory,zur Loye, Hans-Conrad
, p. 169 - 173 (2019)
Abstract: La2USe3S2, exact composition La2USe2.96S2.04, crystallized from a reaction between USe2 and La2S3 in a molten CsCl/KCl eutectic flux and was characterized by single crystal X-ray diffraction. La2USe3S2 crystallizes in the orthorhombic space group Pnma in the U3S5 structure type with lattice parameters a = 12.3284(3)??, b = 8.4028(2)??, and c = 7.3452(2)??. In La2USe3S2 all the anion sites have mixed S and Se occupancy and, henceforth, will be simply referred to as Q sites. The compound exhibits sigmoidal sheets built from LaQ8 (Q = S, Se) bicapped trigonal prisms that edge-share down the a-axis forming rectangular-shaped channels or tunnels. These tunnels are occupied by UQ6 (Q = S, Se) octahedra that edge-share to form infinite, one-dimensional chains running down the b-axis. Graphical Abstract: X-ray diffraction quality single crystals of La2USe3S2 were grown from a molten CsCl/KCl eutectic flux at 950?°C and used for structure determination using single crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group Pnma in the U3S5 structure type.[Figure not available: see fulltext.].
High-pressure X-ray diffraction study of ThOS and UOSe by synchrotron radiation
Gensini, M.,Gering, E.,Benedict, U.,Gerward, L.,Olsen, J. Staun,Hulliger, F.
, p. L9 - L12 (1991)
High-pressure X-ray diffraction studies were performed on ThOS up to 43.3 GPa and on UOSe up to 47.5 GPa, at room temperature, using a diamond anvil cell and synchrotron radiation. The tetragonal structure (P4/nmm) of these compounds was retained over the whole pressure range. The bulk modulus B0 and its pressure derivative B′0 were determined for each compound.
Syntheses and crystal structures of the quaternary uranium lanthanide oxyselenides UYb2O2Se3 and U2Ln 2O4Se3 (Ln=Pr, Sm, Gd)
Raw, Adam D.,Ibers, James A.
, p. 177 - 181 (2012/03/12)
Single crystals of the new uranium lanthanide oxyselenide compounds UYb2O2Se3 and U2Ln2O 4Se3 (Ln=Pr, Sm, Gd) have been synthesized from an Sb 2Se3 flux. The structures have been determined from single-crystal X-ray diffraction data. UYb2O2Se 3 is isostructural to UYb2O2S3. The structure comprises layers of edge-sharing YbSe6 octahedra and double layers of disordered (U/Ln)O4Se4 square antiprisms. The U2Ln2O4Se3 (Ln=Pr, Sm, Gd) compounds are isostructural to U2Ln2O4S3 (Ln=LaGd) whose structure had been deduced previously from X-ray powder diffraction data. In the structure a dodecahedron of four O atoms and four Se atoms surrounds a site primarily occupied by U and a distorted bicapped octahedron of five Se atoms and three O atoms surrounds a site primarily occupied by the lanthanide. These compounds represent the first examples of quaternary uranium oxyselenides.
Synthesis and crystal structure of the γ-modifications of US2 and USe2
Kohlmann,Beck
, p. 785 - 790 (2008/10/09)
We report on γ-US2 and γ-USe2 which may be synthesized by a presumably topotactic reaction from the corresponding U3X5 compounds and elementary chalcogen. γ-USe2 can also be prepared by a high pressure transformation of α-USe2 at 4GPa and 773 K. The structure of the γ phases could be determined and refined by a Rietveld procedure from powder data. They crystallize in an anti-Fe2P-type arrangement. Unusual features of these structures and a possible reaction mechanism for the formation of the compounds are discussed.
