THERMIONIC PROPERTIES OF BAO ON IRIDIUM

The thermionic properties of BaO films on both single and polycrystalline Ir substrates have been measured using Auger, LEED, and thermionic emission microscopy to determine the chemical and structural effects that contribute to these thermionic properties. Measurements were made of the work function (φ) as a function of film thickness, and the temperature dependence of φ for different film thicknesses and substrate orientations. In addition, the effects of nucleation, carbon contamination, as well as evaporation and diffusion on the electron emission from the BaO-Ir system were examined, and quantitative data were obtained on the steady state coverage of BaO on an Ir surface at cathode operating temperatures. A comparison is made between the thermionic properties of the BaO-Ir system and other Ba/BaO-metal systems that have been used in cathodes. © 1979.