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Title: Structure and thermodynamic stability of UTa3O10, aU(v)-bearing compound

Heating a mixture of uranyl(VI) nitrate and tantalum(V) oxide in the molar ratio of 2 : 3 to 1400 °C resulted in the formation of a new compound, UTa3O10. The honey colored to yellow brown crystals of UTa3O10 crystallize in an orthorhombic structure with the space group Fddd (no. 70), lattice parameters a = 7.3947(1), b = 12.7599(2), c = 15.8156(2) Å, and Z = 8. Vertex sharing [TaO6]7– octahedra of two crystallographically distinct Ta cations form a three dimensional tantalate framework. Within this framework, six membered rings of [TaO6]7– octahedra are formed within the (001) plane. The center of these rings is occupied by the uranyl cations [UO2]+, with an oxidation state of +5 for uranium. The pentavalence of U and Ta was confirmed by X-ray photoelectron spectroscopy and X-ray adsorption spectroscopy. The enthalpy of formation of UTa3O10 from Ta2O5, β-U3O7, and U3O8 has been determined to be 13.1 ± 18.1 kJ mol–1 using high temperature oxide melt solution calorimetry with sodium molybdate as the solvent at 700 °C. As a result, the close to zero enthalpy of formation of UTa3O10 can be explained by closely balanced structural stabilizing and destabilizing factors, which may also apply to other UM3O10more » compounds.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [6] ;  [5] ;  [4] ;  [7] ;  [2] ;  [8]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Davis, CA (United States)
  2. Univ. of Notre Dame, Notre Dame, IN (United States)
  3. Nuclear Research Center (Israel)
  4. Univ. of Chicago, Chicago, IL (United States)
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  6. Washington State Univ., Pullman, WA (United States)
  7. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  8. Univ. of California, Davis, CA (United States)
Publication Date:
OSTI Identifier:
1325655
Report Number(s):
LA-UR--16-24811
Journal ID: ISSN 1477-9226; ICHBD9
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Dalton Transactions
Additional Journal Information:
Journal Name: Dalton Transactions; Journal ID: ISSN 1477-9226
Publisher:
Royal Society of Chemistry
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY