Oxygen-18 Tracer Measurements of Anion Diffusion in Uranium Dioxide Thin Films

Joseph R. Bernhardt, Xiaochun Han, Brent J. Heuser

Research output: Contribution to journalArticlepeer-review

Abstract

Oxygen 18 was used as a tracer to quantify anion diffusion in thin-film UO2 using secondary ion mass spectroscopy to measure one-dimensional depth profiles. Both thermal and heavy ion bombardment (1.8 MeV Kr+) treatments were employed over a temperature range from 295 K to 623 K. Textured and single-crystal thin-film samples were grown using reactive-gas magnetron sputtering at ambient temperature. Both microstructures resulted in similar thermal activation energies, Ea= 0.2 eV. This activation energy is significantly lower than the known value for intrinsic anion vacancy-self diffusion in stoichiometric UO2.00 (Ea= 2.5 eV). We attribute this to an interstitialcy mechanism in our hyper-stoichiometric films. The activation energy for irradiated textured films was approximately half that of thermal diffusion, consistent with the chemical rate theory. The opposite was true for the single-crystal microstructure (irradiated Ea= 0.36 eV). This may be due to radiation-induced changes in the microstructure. The mixing parameter was quantified on the anion sublattice as well, ξ = 2.1 ± 0.2 Å5eV−1.

Original languageEnglish (US)
Pages (from-to)4808-4816
Number of pages9
JournalJOM
Volume71
Issue number12
DOIs
StatePublished - Dec 1 2019

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)

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