High-resolution electron microscopy examination of mixed (Cs,Ba)-hollandites reveals evidence for significant short-range order in the distribution of cation vacancies in the incompletely occupied tunnels. The structure was observed to be quite unstable under 400-keV electron irradiation after only a few minutes' study at a dose rate of ca. 104 electrons Å-2 sec-1. Transformations to a microtwinned phase having interaxial angles of 80°/110° rather than 90°, and finally to an amorphous substance, were directly observed and recorded using video techniques. It is evident that hollandites are structurally, chemically, and mechanically unstable under intense electron irradiation. The significance of these observations to the possible effects of self-irradiation in SYNROC preparations, where radioactive 137Cs+1 transmites to 137Ba2+ by electron decay, is discussed.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry