DOI QR코드

DOI QR Code

Advances in High Emission Sc2O3-W Matrix Cathode Materials

  • Wang, Jinshu ;
  • Yang, Yunfei ;
  • Liu, Wei ;
  • Wang, Yiman
  • Received : 2015.12.10
  • Accepted : 2016.02.18
  • Published : 2016.03.30

Abstract

Our work on $Sc_2O_3-W$ matrix dispenser cathodes had been reviewed in this paper. The cathode with uniform distribution of $Sc_2O_3$ had been obtained using liquid-liquid doping method. The cathode had excellent emission property, i.e., the emission current density in pulse condition could reach over $35A/cm^2$. It was found that the cathode surface was covered by a Ba-Sc-O active substance multilayer with a thickness of about 100 nm, which was different from the monolayer and semiconducting layer in thickness. Furthermore, the observation results displayed that nanoparticles appeared at the growth steps and the surface of tungsten grains of the fully activated cathode. The calculation result indicated that the nanoparticles could cause the increase of local electric field strengths. We proposed the emission model that both the Ba-Sc-O multilayer and the nanoparticles distributing mainly on the growth steps of the W grains contributed to the emission. The future work on this cathode has been discussed.

Keywords

$Sc_2O_3$;W;Dispenser cathodes

References

  1. Gaertner G, Geittner P, and Raasch D (2002) Low temperature and cold emission of scandate cathodes. Appl. Surf. Sci. 201, 61-68. https://doi.org/10.1016/S0169-4332(02)00501-9
  2. Gibson J W, Haas G A, and Thomas R E (1989) Investigation of scandate cathodes: emission, fabrication, and activation processes. Electron Devices IEEE Transactions on 36, 209-214. https://doi.org/10.1109/16.21207
  3. Green M C (2008) Cathode technology overview: current status and future directions. In: Proceeding of 2008 IEEE International Vacuum Electronics Conference, Monterey, CA, April 22-24, 2008, pp. 3-4, (IEEE).
  4. Hasker J, Esdonk J V, and Crombeen J E (1986) Properties and manufacture of top-layer scandate cathodes. Appl. Surf. Sci. 26, 173-195. https://doi.org/10.1016/0169-4332(86)90004-8
  5. Liang W, Wang Y, Wang J, Liu W, and Yang F (2014) DC emission characteristic of nanosized-scandia-doped impregnated dispenser cathodes. IEEE Transactions on Electron Devices 61, 1749-1753. https://doi.org/10.1109/TED.2014.2319298
  6. Liu W, Zhang K, Wang Y, Pan K, Gu X, Wang J, Li J, Zhou M (2005) Operating model for scandia doped matrix scandate cathodes. Appl. Surf. Sci. 251, 80-88. https://doi.org/10.1016/j.apsusc.2005.03.197
  7. Oostrom A V and Augustus L (1979) Activation and early life of a pressed barium scandate cathode. Appl. Surf. Sci. 2, 173-186. https://doi.org/10.1016/0378-5963(79)90033-3
  8. Sasaki S, Yaguchi T, Nonaka Y, Taguchi S, and Shibata M (2002) Surface coating influence on scandate cathode performance. Appl. Surf. Sci. 195, 214-221. https://doi.org/10.1016/S0169-4332(02)00557-3
  9. Uda E, Nakamura O, Matsumoto S, and Higuchi T (1999) Emission characteristics of thin-film top-layer scandate cathodes. Ite Technical Report 23, 59-64.
  10. Vancil B, Brodie I, Lorr J, and Schmidt V (2014) Scandate dispenser cathodes with sharp transition and their application in microwave tubes. IEEE Transactions on Electron Devices 61, 1754-1759. https://doi.org/10.1109/TED.2014.2309279
  11. Wan C and Kordesch M E (2013) Tungstate formation in a model scandate thermionic cathode. Journal of Vacuum Science & Technology B Microelectronics & Nanometer Structures, 31, 011210-011210-11. https://doi.org/10.1116/1.4772007
  12. Wang J, Chen L, Liu W, Yang F, Zhang X, Cui Y, and Zhou M (2013) Effect of scandia doping method on the emission uniformity of scandate cathode with $Sc_2O_3$-W matrix. Materials Research Bulletin 48, 3594-3600. https://doi.org/10.1016/j.materresbull.2013.05.069
  13. Wang J, Cui Y, Liu W, Wang Y, Yang F, Zhou F, and Zhou M (2015) A study of scandia-doped-impregnated cathode fabricated by spray drying method. IEEE Transactions on Electron Devices, 62, 1635-1640. https://doi.org/10.1109/TED.2015.2412153
  14. Wang J, Li L, Liu W, Wang Y, Wang Y, and Zhou M (2008a) $Sc_2O_3$-W matrix impregnated cathode with spherical grains. Journal of Physics & Chemistry of Solids 69, 2103-2108. https://doi.org/10.1016/j.jpcs.2008.03.013
  15. Wang J, Wang Y, Liu W, Li L, Wang Y, and Zhou M (2008b) Emission property of scandia and re doped tungsten matrix dispenser cathode. Journal of Alloys & Compounds 459, 302-306. https://doi.org/10.1016/j.jallcom.2007.04.247
  16. Wang Y, Wang J, Liu W, Li L, Wang Y, and Zhang X (2009) Correlation between emission behavior and surface features of scandate cathodes. IEEE Transactions on Electron Devices, 56, 776-785. https://doi.org/10.1109/TED.2009.2015619
  17. Wang Y, Wang J, Liu W, Zhang K, and Li J (2007) Development of high current-density cathodes with scandia-doped tungsten powders. Electron Devices IEEE Transactions on, 54, 1061-1070. https://doi.org/10.1109/TED.2007.894602
  18. Yamamoto S, Taguchi S, Aida T, and Kawase S (1984a) Study of metal film coating on $Sc_2O_3$ mixed matrix impregnated cathodes. Appl. Surf. Sci. 17, 517-529. https://doi.org/10.1016/0378-5963(84)90011-4
  19. Yamamoto S, Taguchi S, Aida T, Oi T, and Kawase S (1984b) Electron emission properties and surface atom behavior of impregnated cathodes with rare earth oxide mixed matrix base metals. Appl. Surf. Sci. 20, 69-83.
  20. Yamamoto S, Taguchi S, Watanabe I, and Kawase S (1986) Electron emission properties and surface atom behavior of an impregnated cathode coated with tungsten thin film containing $Sc_2O_3$. Japanese Journal of Applied Physics.pt Regular Papers & Short Notes 25, 971-975.