Preparation of W–Sc2O3 targets and scandate cathodes with film prepared by pulsed laser deposition

Abstract

Sub-micrometer Sc2O3–W powder with a narrow particle size distribution has been obtained by a sol–gel method combined with two-step hydrogen reduction process. Based on the obtained powder, the W–Sc2O3 targets have been sintered via spark plasma sintering (SPS) at 1300°C. The W–Sc2O3 targets have the average grain size of about 1μm. Both the sintering temperature and holding time are much lower than those of the targets prepared with micrometer sized powders. The obtained W–Sc2O3 targets have a high comparative density of 96.4% and rockwell hardness of 86.4 HRC. Using the target, the scandate cathode deposited with a film containing 5% Sc2O3 and 95% W has been obtained by pulsed laser deposition (PLD) method. This cathode has good emission property, i.e., the highest thermionic emission current density reaches 43.09A/cm2 of Jdiv at 900°Cb after being activated for 8h, which is much higher than that of scandate cathode without film. Scandium (Sc) supplied by the film on the surface during the activation forms a Ba–Sc–O active layer, which helps to the emission.