Energetics of a uranothorite (Th1-xUxSiO4) solid solution

Xiaofeng Guo, Stéphanie Szenknect, Adel Mesbah, Nicolas Clavier, Christophe Poinssot, Di Wu, Hongwu Xu, Nicolas Dacheux, Rodney C. Ewing, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO4)x-(ThSiO4)1-x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. However, variations in unit cell parameters and negative excess volumes of mixing, coupled with strongly exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.

Original languageEnglish (US)
Pages (from-to)7117-7124
Number of pages8
JournalChemistry of Materials
Volume28
Issue number19
DOIs
StatePublished - Oct 11 2016
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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