A study of an oxide-coated cathode with the electron microscope
The relation between the thermionic electron emission and the surface structure or crystallite size of the oxide cathode material is a problem of interest for physicists as well as for engineers. Oxide cathodes, however, are extremely unstable in the atmosphere, whereas only a mean size is measured in vacuum by the X-ray diffraction method, as used by Eisenstein (1), Rooksby (2), Wright (3) and Yamaka (4). Recently, in Japan, Yazawa and Yako (5) and Hirota (6) have investigated a replica method which can fix the state of the cathode surface in vacuum. On the other hand, oxide cathodes during decomposition were directly observed in the electron microscope with a special specimen-chamber by Ueda (7).
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