ION-BOMBARDMENT-INDUCED RADIATION DAMAGE IN SOME CERAMICS AND IONIC CRYSTALS: DETERMINED BY ELECTRON DIFFRACTION AND GAS RELEASE MEASUREMENTS

Abstract

Single-crystal specimens or polycrystalline sinters of cubic NaCl, KCl, KBr, KI, MgO, CaO, NiO, UC, CaF 2 , BaF 2 , UO 2 , and ThO 2 as well as anisotropic TiO 2 , Al 2 O 3 , and U 3 O 8 were bombarded with 40-keV xenon or krypton ions to give integrated ion doses of up to 2 × 10 16 ions/cm 2 . The specimens were examined by reflection electron diffraction for radiation damage in the form of a phase change from the crystalline to a quasi-amorphous state (metamictization). Damage of this kind was observed in all anisotropic crystals; observable lattice disorder without phase change was obtained for MgO. None of the other cubic materials showed any appreciable change in their diffraction pattern, even at the highest dose. The annealing of the disorder in the lattice was correlated with release of the gas at low temperatures for all damaged substances. Significant gas releases at low temperatures were also obtained when much of the gas was in close proximity to the surface. Some other experimental conditions that cause gas release at low temperature are discussed.