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Powder Metallurgy and Metal Ceramics

, Volume 44, Issue 11–12, pp 598–607 | Cite as

Effect of microstructure on the mechanism of emission for tungsten-barium dispenser cathodes

  • O. I. Get’man
  • A. E. Lushkin
  • V. V. Panichkina
  • S. P. Rakitin
Article

Abstract

The effect of tungsten powder fineness and microstructure parameters of the tungsten skeleton on the emission of dispenser cathodes (DC) in the stages of degassing and high-temperature activation are studied. Quantitative analysis of the cathode surface microstructure is investigated. It is established that the work function of the DC after high-temperature activation does not depend upon the size of tungsten powder particles in the test range of fineness (average particle size 1.4–20 μm) and porosity of the tungsten skeleton (22 and 35%). The time for reaching the maximum DC activity increases with an increase in particle size and skeleton porosity. The highest emission uniformity is exhibited by cathodes with a uniform microstructure prepared from tungsten powder with an average size of 1 and 4 μm. It is shown that the DC emission capacity is connected with the marked three-dimensional structure of BaO-CaO at the cathode surface, and also monatomic films (Ba-O and Ba) and excess oxygen at the surface of the tungsten phase.

Keywords

tungsten-barium dispenser cathode tungsten powder emission capacity degassing activation work function 

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Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  • O. I. Get’man
    • 1
  • A. E. Lushkin
    • 1
  • V. V. Panichkina
    • 1
  • S. P. Rakitin
    • 1
  1. 1.Institute for Problems of Materials ScienceNational Academy of Sciences of UkraineKiev

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