High Current Density and Long-Life Nanocomposite Scandate Dispenser Cathode Fabrication

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: similar to 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 degrees C and 170 +/- 5 A . cm(-2) at 1050 degrees 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 degrees C after 10680 h.