Trapping helium in Y{sub 2}Ti{sub 2}O{sub 7} compared to in matrix iron: A first principles study

Journal Article · Mon Apr 14 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4871282· OSTI ID:22273616

Yang, Litong ^[1]; Jiang, Yong ^[1]; Yamamoto, Takuya ^[2]; Liu, Zuming; Liu, Yong ^[3]

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1. School of Materials Science and Engineering, Central South University, Changsha 410083 (China)
2. Materials Department, University of California, Santa Barbara, California 93106 (United States)
3. State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083 (China)

Pyrochlore Y{sub 2}Ti{sub 2}O{sub 7} is a primary precipitate phase in nano-structured ferritic alloys (NFAs) for fission and fusion energy applications. We report a theoretical study for assessing the relative stability of trapping helium in Y{sub 2}Ti{sub 2}O{sub 7} versus in matrix iron. Various defect structures and the associated energies are examined and compared. Results reveal that helium can be deeply trapped in Y{sub 2}Ti{sub 2}O{sub 7} and that the corresponding self-interaction is essentially repulsive. Transmutant helium in NFAs prefers to occupy individual octa-interstitial sites in Y{sub 2}Ti{sub 2}O{sub 7}, before forming small clusters in Y{sub 2}Ti{sub 2}O{sub 7}. Helium partitioning in NFAs depends on the number and dispersion of Y{sub 2}Ti{sub 2}O{sub 7}; and thus initially, bubble formation and growth in iron matrix can be largely suppressed. Charge transfer occurs from helium to neighboring oxygen anions, but not to neighboring metal cations, suggesting a general effectiveness of trapping helium in oxides. Reasons for the ultimate fate of helium to form small nm-scale interface bubbles are also discussed.

• OSTI ID: 22273616
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
77 NANOSCIENCE AND NANOTECHNOLOGY
ANIONS
CATIONS
COMPARATIVE EVALUATIONS
FERRITIC STEELS
HELIUM
INTERFACES
IRON
MATRIX MATERIALS
NANOSTRUCTURES
PHASE STABILITY
PRECIPITATION
TITANIUM OXIDES
TRAPPING
YTTRIUM COMPOUNDS