Title :
High Current Density and Long-Life Nanocomposite Scandate Dispenser Cathode Fabrication
Author :
Zhao, Jinfeng ; Li, Na ; Li, Ji ; Barnett, Larry R. ; Banducci, Mike ; Gamzina, Diana ; Munir, Zuhair A. ; Luhmann, Neville C.
Author_Institution :
Dept. of Appl. Sci., Univ. of California, Davis, CA, USA
fDate :
4/1/2011 12:00:00 AM
Abstract :
A nano-Sc2O3-added W powder for use in high current density thermionic cathodes has been made using a solution-gel method with the following controllable uniform average particle sizes: ~72, 146, 272, and 587 nm. Using these powders, nanostructured Sc2O3 -added tungsten matrices with uniform nanosized tungsten grains and homogenous pore distribution were obtained. Nanocomposite Sc2O3-added W impregnated cathodes have been prepared from these powders and have shown excellent emission properties. For example, space-charge-limited current densities of 40 ± 1 A · cm-2 at 850°C and 170 ± 5 A · cm-2 at 1050°C have been obtained using a 300-nm Sc2O3-added (4.77 wt.%) W powder. Life testing is ongoing with 50 ± 2.5 A · cm-2 current density emission demonstrated at 1050°C after 10 680 h.
Keywords :
cathodes; current density; nanocomposites; nanofabrication; nanoparticles; particle reinforced composites; porosity; porous materials; powders; scandium compounds; sol-gel processing; tungsten; Sc2O3-W; current density; emission properties; homogenous pore distribution; impregnated cathodes; life testing; long-life nanocomposite; nanosized tungsten grains; powder; scandate dispenser cathode fabrication; size 300 nm; solution-gel method; space-charge-limited current densities; temperature 1050 degC; temperature 850 degC; thermionic cathodes; time 10680 h; tungsten matrices; Cathodes; Current density; Grain size; Heating; Powders; Testing; Tungsten; $hbox{Sc}_{2}hbox{O}_{3}$-added W; Current density; nanosize;
Journal_Title :
Electron Devices, IEEE Transactions on
DOI :
10.1109/TED.2011.2109723
