Structure and thermodynamic stability of UTa3O10, a U(V)-bearing compound

Xiaofeng Guo; Christian Lipp; Eitan Tiferet; Antonio Lanzirotti; Matthew Newville; Mark H. Engelhard; Di Wu; Eugene S. Ilton; Stephen R. Sutton; Hongwu Xu; Peter C. Burns; Alexandra Navrotsky

doi:10.1039/C6DT02843H

Structure and thermodynamic stability of UTa₃O₁₀, a U(v)-bearing compound†

Xiaofeng Guo,

^ab Christian Lipp,^c Eitan Tiferet,^d Antonio Lanzirotti,^e Matthew Newville,^e Mark H. Engelhard,^f Di Wu,

^g Eugene S. Ilton,^h Stephen R. Sutton,^ei Hongwu Xu,^a Peter C. Burns^cj and Alexandra Navrotsky*^b

Author affiliations

* Corresponding authors

^a Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

^b Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, California 95616, USA
E-mail: anavrotsky@ucdavis.edu

^c Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, Indiana 46556, USA

^d Nuclear Research Center – Negev Be'er-Sheva 84190, Israel Institution, Israel

^e Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, USA

^f Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, USA

^g The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, USA

^h Pacific Northwest National Laboratory, Richland, Washington 99352, USA

ⁱ Department of Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA

^j Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA

Abstract

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. 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.

Dalton Transactions

Structure and thermodynamic stability of UTa₃O₁₀, a U(v)-bearing compound†

Abstract

Supplementary files

Article information

Download Citation

Permissions

Structure and thermodynamic stability of UTa₃O₁₀, a U(V)-bearing compound

Social activity

Search articles by author

Spotlight

Advertisements

Dalton Transactions