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Title: Energetics of a uranothorite (Th1–xUxSiO4) solid solution

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. Furthermore, 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.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [2] ;  [6] ;  [7]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Davis, CA (United States)
  2. CNRS/CEA/Univ. of Montpellier/ENSCM, Bagnols sur Ceze cedex (France)
  3. CEA, Bagnols sur Ceze (France)
  4. Washington State Univ., Pullman, WA (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. Stanford Univ., Stanford, CA (United States)
  7. Univ. of California, Davis, CA (United States)
Publication Date:
OSTI Identifier:
1329910
Report Number(s):
LA-UR--16-26227
Journal ID: ISSN 0897-4756
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 28; Journal Issue: 19; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
LDRD; USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY