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

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)18892-18899
Number of pages8
JournalDalton Transactions
Volume45
Issue number47
DOIs
StatePublished - 2016
Externally publishedYes

ASJC Scopus subject areas

  • Inorganic Chemistry

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