MICROSCOPY Vol.46▶No.3 2011
â– Feature Articles: New Trends and Prospects in High Voltage Electron Microscopy

Nature of Dislocation Loops in Fluorite Structure Oxides and the Role of Selective Displacement Damage

Kazuhiro Yasuda, Kazufumi Yasunaga, Kenichi Shiiyama and Syo Matsumura

Abstract: Oxides with fluorite structure are known as radiation tolerant ceramics, and have potential applications to advanced fuels of light water reactors, and to inert matrix for the burning and transmutation of minor actinoids and long-lived fission products. This paper reports the nucleation-and-growth of dislocation loops in fluorite structure oxides, such as ceria and yittria stabilized cubic zirconia, formed under electron irradiation. Transmission electron microscopy analysis has shown that the nature of dislocation loops strongly depends on electron energy: dislocation loops formed by energetic electrons less than around 1.3 MeV was found to be faulted dislocation loops consist of oxygen ions lying on {111} planes, and they have revealed anomalous growth process and multiplied dislocations when their size reached at a critical size. On the other hand, perfect dislocation loops on {110} planes were formed at higher electron energies where elastic displacements were induced on both cation and anion sublattice. A role of the selective displacement damage in oxygen sublattice was discussed based on the analysis on TEM images and results obtained by molecular dynamic simulations.

Key words: Oxide ceramics with fluorite structure, Radiation damage Selective displacement damage, Dislocation loops, In situ observations under electron irradiation