Surface studies on the low work function surface complex of barium on an osmium-ruthenium substrate |
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| Institution: | 1. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi''an 710072, China;2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;1. College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, PR China;2. School of Materials Science and Engineering, Xi''an University of Technology, Xi''an 710048, PR China;1. Department of Production Technology, Faculty of Industrial Education, Helwan University, 30 El Sawah Street, 11511-11668 Cairo, Egypt;2. Department of Mechanical Engineering, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182, USA |
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| Abstract: | Barium and oxygen on an osmium-ruthenium (Os/Ru) surface is the surface complex responsible for the excellent electron emission properties of commercial M-type thermionic cathodes. A computerized Auger technique was used to study the surface properties of this surface complex and compare it with results obtained earlier for Ba-O-W surfaces, which characterize the properties of commercial barium impregnated tungsten thermionic cathodes. Barium desorption, electron emission and barium, barium oxide evaporation were measured at elevated temperatures for this experimental surface study. Desorption measurements, at 1100°C, on the barium on osmium-ruthenium substrate show that the energy for desorption was higher than that for the lowest work function Ba-O-W surface (5.4 to 4.8 eV). Oxygen was always present on the sputtered Os/Ru substrate and contributed to the strong bonding of barium to the Os/Ru surface. The barium and barium oxide evaporative products from such a surface at 1100°C were found to be mainly barium with the Ba/BaO ratio equal to approximately 100. |
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