Radiation-enhanced diffusion of oxygen-18 in uranium dioxide thin films

Anion radiation enhanced diffusion (RED) and thermal diffusion of a buried 18O tracer layer in thin film UO2 was measured using Secondary-Ion Mass Spectroscopy (SIMS). Thin films were grown using a dedicated magnetron sputtering chamber. Samples were irradiated with 1.8 MeV Kr+ over a temperature range from 295 K to 623 K. Measurements have been made for both single crystal and textured films. This difference in crystal structure led to significantly different results. Thin film stoichiometry was also shown to have an effect on RED and thermal diffusion. For RED, activation energies found from best fit analysis were Ea = 0.83 and Ea = 0.37, for single crystal and textured samples, respectively. RED for single crystal UO2 thin films can be represented by, D_RED=8.7×〖10〗^(-14) exp⁡((-0.83)/kT) 〖cm〗^2/sec RED for textured UO2 thin films can be represented by, D_RED=2.0×〖10〗^(-15) exp⁡((-0.37)/kT) 〖cm〗^2/sec Thermal diffusion measurements resulted, from best fit analysis, in similar activation energies for single crystal and textured thin films, Ea = 0.46 and Ea = 0.53, respectively. This was shown to agree well with published experimental and calculated values for UO2-x for anion vacancies. Thin films used in this work were thought to be substoichiometric and thermal diffusion is thought to be controlled by anion vacancies. Mixing parameter measurements found ξ = 2.1 ± 0.2〖 Å〗^5 〖eV〗^(-1) on the anion sublattice, which indicated that ballistic mixing was the dominant mechanism of ion-mixing and that thermal spike activity is negligible.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2013

Author dc:creator

• Bernhardt, Joseph

Contributors dc:contributor

• Heuser, Brent J.

• Radiation-enhanced diffusion (RED)
• UO2
• Anion Diffusion
• Uranium dioxide thin films

Statement dc:rights

• Copyright 2013 Joseph R. Bernhardt

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/45289

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/45289