17.5: High current density and long life nanocomposite scandate dispenser cathode fabrication

Sc₂O₃-doped W powder for use in high current density thermionic cathodes has been made by the sol-gel method with different particle sizes. Sc₂O₃-W matrix cathodes have been prepared from these powders, and have shown excellent emission properties. A space charge limited current density of 80 A/cm² at 1150°C, 50 A/cm² at 1050°C have been obtained by using 500 nm Sc₂O₃-doped W powders. Life testing is ongoing with a continuously pulsed loading of 50 A/cm² at 1050°C after 5448 hours. The maximum current density of the cathode made from 1-2 micro size S_c2O₃-doped W powder can reach 106 A/cm² at 1150°C.