Radiation-induced effects in pyrochlores and nanoscale materials engineering

Abstract

Pyrochlore materials, A2B2O7, encompass a wide range of compositions and are technologically important for energy and environmental issues. For example, they may be used as ionic conductors in solid oxide fuel cells or nuclear waste forms for the storage of actinides, particularly Pu. Here, the recent progress in understanding ion beam irradiation-induced phenomena in pyrochlore compounds is briefly reviewed with a focus on the ion beam-induced crystalline-to-amorphous and pyrochlore-to-fluorite structural transitions. Systematic ion irradiation studies of lanthanide pyrochlores with B=Ti, Zr and Sn have indicated that the radiation response of the pyrochlore compounds is highly dependent on compositional changes. Both the ionic size and cation electronic configurations (e.g. bond-types) affect the structural distortion from the ideal fluorite structure and thus the response of pyrochlore-structure types to ion beam irradiation. An ion beam-induced pyrochlore-to-fluorite structural transition occurs in all irradiated pyrochlore compositions, and the independent kinetics of the cation and anion disordering processes has been discussed. Numerous novel nanostructures have been created by utilizing the ion beam-induced amorphization, order–disorder transition and phase decomposition, such as amorphous and disordered nano-domains, perfectly lattice matched two-dimensional nanolayers, self-organized ripple structures, metallic nanoparticles and nanowires.