Structure and bulk modulus of Ln-doped UO₂ (Ln = La, Nd) at high pressure

Journal Article · 10 April 2017 · Journal of Nuclear Materials

DOI: https://doi.org/10.1016/j.jnucmat.2017.04.007 · OSTI ID:1369255

Rittman, Dylan R.  ^[1]; Park, Sulgiye ^[1]; Tracy, Cameron L.  ^[1]; Zhang, Lei ^[2]; Palomares, Raul I.  ^[3]; Lang, Maik ^[3]; Navrotsky, Alexandra ^[2]; Mao, Wendy L. ^[4]; Ewing, Rodney C. ^[1]

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1. Stanford Univ., Stanford, CA (United States)
2. Univ. of California, Davis, CA (United States)
3. Univ. of Tennessee, Knoxville, TN (United States)
4. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

The structure of lanthanide-doped uranium dioxide, Ln_xU_1-xO_2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO₂, such as Young's modulus.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC02-76SF00515; SC0001089; NA0001974; FG02-99ER45775; AC02-05CH11231; EAR 1606856; NA0002006
• OSTI ID: 1369255
• Alternate ID(s): OSTI ID: 1419350
• Journal Information: Journal of Nuclear Materials, Vol. 490, Issue C; ISSN 0022-3115
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English

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