Krypton irradiation damage in Nd-doped zirconolite and perovskite

摘要

Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts\udfor plutonium disposition is necessary to evaluate their long-term behaviour during geological disposal.\udPolycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex situ with\ud2 MeV Kr+ at a dose of 5 1015 ions cm2 to simulate recoil of Pu nuclei during alpha decay. The feasibility\udof thin section preparation of both pristine and irradiated samples by Focused Ion Beam sectioning\udwas demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region\udseparated from the pristine material by a thin (40–60 nm) damaged interface. The zirconolite lattice was\udlost in the damaged interface, but the fluorite sublattice was retained. The Nd-doped perovskite contained\uda defined irradiated layer composed of an amorphous region surrounded by damaged but still\udcrystalline layers. The structural evolution of the damaged regions is consistent with a change from\udorthorhombic to cubic symmetry. In addition in Nd-doped perovskite, the amorphisation dose depended\udon crystallographic orientation and possibly sample configuration (thin section or bulk). Electron Energy\udLoss Spectroscopy revealed Ti remained in the 4+ oxidation state but there was a change in Ti coordination\udin both Nd-doped perovskite and Nd-doped zirconolite associated with the crystalline to amorphous\udtransition.