Study and Development of Yttrium-Doped Nanoscandate Cathode for High-Power VEDs

Nanoscandate cathode (NSC) has several advantages over a conventional scandate cathode in terms of emission uniformity, resistance to ion bombardment, and long life. In the present technology of “Yttrium-doped NSC,” yttrium oxide (Y 2 O 3 ) is codoped with tungsten powder, scandium oxide, and other impregnant materials to make nanopowder using the solgel technique. The pellets, made out of powder, were integrated with potted heaters. The cathodes were analyzed in an analytical chamber containing: 1) Auger electron spectroscopy for surface analysis; 2) anode for emission measurements; and 3) thermionic emission microscope (THEM) for studying emission uniformity. It was found that by adding a small amount of yttrium oxide of 3%–5% by weight increases the emission uniformity of cathode significantly as observed through THEM. Emission current density of more than 80 A/cm 2 was drawn from these cathodes under deep space charge conditions.