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Title: Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd)

Abstract

Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

Authors:
;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1386619
DOE Contract Number:  
SC0001089
Resource Type:
Journal Article
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 465; Journal Issue: C; Related Information: MSA partners with University of Notre Dame (lead); University of California, Davis; Florida State University; George Washington University; University of Michigan; University of Minnesota; Oak Ridge National Laboratory; Oregon state University; Rensselaer Polytechnic Institute; Savannah River National Laboratory; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; nuclear (including radiation effects), materials and chemistry by design, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Zhang, Lei, and Navrotsky, Alexandra. Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd). United States: N. p., 2015. Web. doi:10.1016/j.jnucmat.2015.06.059.
Zhang, Lei, & Navrotsky, Alexandra. Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd). United States. doi:10.1016/j.jnucmat.2015.06.059.
Zhang, Lei, and Navrotsky, Alexandra. Thu . "Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd)". United States. doi:10.1016/j.jnucmat.2015.06.059.
@article{osti_1386619,
title = {Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd)},
author = {Zhang, Lei and Navrotsky, Alexandra},
abstractNote = {Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.},
doi = {10.1016/j.jnucmat.2015.06.059},
journal = {Journal of Nuclear Materials},
issn = {0022-3115},
number = C,
volume = 465,
place = {United States},
year = {2015},
month = {10}
}