Structure and thermodynamic stability of UTa3O10, aU(v)-bearing compound
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Davis, CA (United States)
- Univ. of Notre Dame, Notre Dame, IN (United States)
- Nuclear Research Center (Israel)
- Univ. of Chicago, Chicago, IL (United States)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Washington State Univ., Pullman, WA (United States)
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Univ. of California, Davis, CA (United States)
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 UM3O10 compounds.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1325655
- Report Number(s):
- LA-UR-16-24811; ICHBD9
- Journal Information:
- Dalton Transactions, Journal Name: Dalton Transactions; ISSN 1477-9226
- Publisher:
- Royal Society of ChemistryCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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