Papers by Author: Kazuhiro Yasuda

Abstract: Characteristic features of radiation damage in insulators for fusion reactors are that those materials are exposed to synergistic radiation damage of elastic displacements and electric excitation with the presence of an electric field. This paper describes the nucleation-and-growth of radiation-induced defects and their stability in oxide ceramics, such as magnesium-aluminate spinel (MgAl2O4) and alpha-alumina (α-Al2O3). Microstructure evolution in these oxides is shown through transmission electron microscopy for the formation process of dislocation loops under synergistic irradiation with displacements and ionizing radiation, the stability of dislocation loops, and the nucleation-and-growth process of loops with an applied electric field.

Abstract: We report the formation of anomalous defect clusters in yttria stabilized zirconia (YSZ: 13 mol% Y2O3-ZrO2), which are a primary candidate for inert matrix fuels. Electron irradiation with 100 to 1000 keV is found to induce characteristic defect clusters. The defect clusters show strong black/black lobes contrast and multiply dislocations when the defect clusters grow to a critical diameter of 1.0-1.5 µm. Our analysis with transmission electron microscopy and numerical calculations lead to a conclusion that these defect clusters are charged oxygen platelets formed by the selective displacements of oxygen sublattice.