Irradiation-induced defects in β''-alumina examined by 1 MV high-resolution electron microscopy

The defect blocks formed in β''-alumina by electron irradiation are examined by 1 MV high-resolution electron microscopy. In order to explain the fact that two distinctly different types of defect images appear even in a single 1 MV micrograph, a new structural model is constructed in place of the two models so far reported. In the model proposed, two spinel-like blocks on either side of the eliminated conduction plane are directly combined by the vectors including x, y components to form cubic close packing of oxygen layers in the resultant defect blocks. The arrangements of cations in the defect block are slightly different from those expected from the spinel structure.