Radiation Damage inβ″-Alumina Observed with High Resolution Electron Microscope
Wen Shulin Song Xiangyun Lin Zuxiang Chen Kungang (Shanghai Institute of Ceramics,Academia Sinica)
The β″-alumina is an important fast ion conductor.The conductive ions are Na~+from conduction layers in the structure.Its chemical formula is Na_2O·5Al_2O_3.Itbelongs to trigonal system with space group R(?)m.Its lattice parameters are a=5.614(?),c=33.85(?).A unit cell contains three spinel-like blocks alternated with three Na~+conduction layers.Using HREM,Yoshio Matsui and Shigeo Horiuche have observed that underradiation of electron beam,Na~+ conduction layers in β″-alumina disappear,and twospinel-like blocks nearby directly combine.We have observed this phenomenon not onlyfrom high resolution lattice image but also from the electron diffraction image.Moreover,under the radiation of electron beam,we have also found the superstructuresin which three or four spinel-like blocks and Na~+ conduction layers have been damagedsimultaneously,and that electron radiation damage in β″-Al_2O_3 is closely related tosome defects in the material.The electron beam radiation produces point defects,thesepoint defects quicken the radiation damage in return,even in some areas of thespecimen appears the tendency of disordering.