Identification of NpO2+x in the binary Np-O system
Abstract
In contrast to UO2 and PuO2, there is no consensus on the existence of mixed valence NpO2+x, resulting in a gap between NpO2 and Np2O5 (the highest binary oxide of Np) in the Np-O phase diagram. We now show NpO2+x via Np LIII Extended X-ray Absorption Fine Structure (EXAFS) spectra of three samples of NpO2 that, analogous to U and Pu, exhibit multisite Np-O distributions with varying numbers of oxygen atoms at 1.87–1.91 Å. Furthermore this is supported by the diffraction pattern of the sample with the largest amount of this oxo-type species that can be refined with both the simple fluorite structure and a trigonal one related to α-U4O9. The implied Np(V)-bridging oxo moieties as well as possible indications of OH- found by detailed EXAFS analysis suggest that NpO2+x more closely resembles PuO2+x than UO2+x. An additional common characteristic suggested by the EXAFS and X-Ray Diffraction (XRD) is the phase separation into NpO2 and what would be previously unreported Np4O9(-δ), indicative of O clustering.
- Authors:
-
- Synchrotron SOLEIL, Gif-sur-Yvette Cedex (France)
- Josef Stefan Institute, Ljubljana (Slovenia); Washington State Univ., Pullman, WA (United States)
- Chatenay-Malabry and CEA/DEN/DANS/DMN/SRMA/LA2M-LRC CARMEN, Gif-sur-Yvette (France)
- Devi Ahilya Vishwavidyalaya, Indore (India)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Publication Date:
- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
- OSTI Identifier:
- 1510745
- Alternate Identifier(s):
- OSTI ID: 1396913
- Grant/Contract Number:
- AC02-05CH11231
- Resource Type:
- Journal Article: Accepted Manuscript
- Journal Name:
- Journal of Nuclear Materials
- Additional Journal Information:
- Journal Volume: 490; Journal Issue: C; Journal ID: ISSN 0022-3115
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE
Citation Formats
Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., and Shuh, David K. Identification of NpO2+x in the binary Np-O system. United States: N. p., 2017.
Web. doi:10.1016/j.jnucmat.2017.04.019.
Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., & Shuh, David K. Identification of NpO2+x in the binary Np-O system. United States. https://doi.org/10.1016/j.jnucmat.2017.04.019
Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., and Shuh, David K. 2017.
"Identification of NpO2+x in the binary Np-O system". United States. https://doi.org/10.1016/j.jnucmat.2017.04.019. https://www.osti.gov/servlets/purl/1510745.
@article{osti_1510745,
title = {Identification of NpO2+x in the binary Np-O system},
author = {Tayal, Akhil and Conradson, Steven D. and Baldinozzi, Gianguido and Namdeo, Sonu and Roberts, Kevin E. and Allen, Patrick G. and Shuh, David K.},
abstractNote = {In contrast to UO2 and PuO2, there is no consensus on the existence of mixed valence NpO2+x, resulting in a gap between NpO2 and Np2O5 (the highest binary oxide of Np) in the Np-O phase diagram. We now show NpO2+x via Np LIII Extended X-ray Absorption Fine Structure (EXAFS) spectra of three samples of NpO2 that, analogous to U and Pu, exhibit multisite Np-O distributions with varying numbers of oxygen atoms at 1.87–1.91 Å. Furthermore this is supported by the diffraction pattern of the sample with the largest amount of this oxo-type species that can be refined with both the simple fluorite structure and a trigonal one related to α-U4O9. The implied Np(V)-bridging oxo moieties as well as possible indications of OH- found by detailed EXAFS analysis suggest that NpO2+x more closely resembles PuO2+x than UO2+x. An additional common characteristic suggested by the EXAFS and X-Ray Diffraction (XRD) is the phase separation into NpO2 and what would be previously unreported Np4O9(-δ), indicative of O clustering.},
doi = {10.1016/j.jnucmat.2017.04.019},
url = {https://www.osti.gov/biblio/1510745},
journal = {Journal of Nuclear Materials},
issn = {0022-3115},
number = C,
volume = 490,
place = {United States},
year = {Fri Apr 14 00:00:00 EDT 2017},
month = {Fri Apr 14 00:00:00 EDT 2017}
}
Web of Science
Figures / Tables:
Figures / Tables found in this record: