Nanostructured materials with grain sizes well below 100 nm are revolutionizing technology advances due to their exceptional size-dependent control of chemical, physical, electrical and optical properties. Cubic ceria and zirconia are well known ionic conductors that are also isostructural with urania, plutonia, and thoria nuclear fuels, and zirconia is a potential inert fuel matrix. In the context of nuclear fuels and inert matrices, cubic ceria and zirconia are model systems for evaluating the role of nanograined structures on radiation effects. The ability to control and engineer materials by ion beams may also be critical to developing clean energy sources.

We have studied the response of nanocrystalline cubic ceria and zirconia to ion-beam irradiation. Nanocrystalline ceria and zirconia films were prepared by ion-beam-assisted deposition that produced nanostructurally-stabilized pure cubic ceria and zirconia with grain sizes of about 8 nm. The films were irradiated with MeV Au ions at 160 to 400 K to doses corresponding to 35 displacements per atom. The average grain size was determined by grazing incident X-ray diffraction. The rate of grain growth follows a power law dependence (n=6) to a saturation grain size that decreases with temperature and is intrinsically different from thermally-activated grain growth (n=2) or that reported in metals under irradiation (n=3). While the cubic phase is retained, some reduction of O in the irradiated films is indicated from Rutherford backscattering spectroscopy measurements. Transmission electron microscopy observations and selected area electron diffraction have also confirmed the grain growth and stability of the cubic phase.

William J Weber*, University of Tennessee, Oak Ridge National Laboratory, United States
Yanwen Zhang, Pacific Northwest National Laboratory, United States
Weilin Jiang, Pacific Northwest National Laboratory, United States
Philip Edmondson, Pacific Northwest National Laboratory, United States
Sandra Moll, Pacific Northwest National Laboratory, United States
Fereydoon Namavar, University of Nebraska Medical Center, United States

*presenting author