Electron Microscope Study of the Decomposition Process of Oxide Coated Cathodes

Electron microscope observation on oxide coated cathode is undertaken especially on its decomposition process and on the prolonged heat treatment. A new replica method which is used in this study is as follows; (1) deposition of SiO film at first on the specimen, (2) pressing the SiO-evaporated-specimen onto ethylmethacrylate resin film, (3) shadowing by germanium evaporation and (4) reinforcing with carbon film. This replica technique enables us to observe the exact surface structure of oxide cathode, which has a porous surface and which is very unstable in the atomosphere. About the decomposition process, following results are obtained: Growth of the oxide crystal becomes significant at a certrin decomposition–temperature. For “triple carbonate”, this critical temperature lies at around 1100°C. With the “single carbonate”, crystal growth occurs at considerably lower temperature than with the triple.