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

• W–Sc2O3 film containing 5% Sc2O3 and 95% W were prepared by pulsed laser deposition.
• W–Sc2O3 film on scandate cathode surface improves emission property.
• The film improves Sc distribution uniformity and is favorable for forming Ba–Sc–O layer.

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 1 μm. 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 43.09 A/cm2 of Jdiv at 900 °Cb after being activated for 8 h, 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.

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