A study of Eu2O3, Sc2O3 co-doped tungsten matrix impregnated cathode

Eu2O3 and Sc2O3 co-doped W matrix impregnated cathodes have been prepared by the powder metallurgy method. The constitution of active elements on activated cathode surface is analyzed by in-situ Auger electron spectroscopy. It is found that although Eu exists in the matrix, no Eu is found on the cathode surface due to the formation of a stable Eu containing compound. Sc, Ba and O diffuse to the surface of the cathode and form an active surface layer during the activation period whereas the stable Eu-compound cannot liberate free Eu, which can diffuse from the cathode to the surface. The active substance of Sc, Ba and O on the cathode surface contribute to the emission property.

► Eu2O3 and Sc2O3 co-doped W matrix impregnated cathode showed higher emission propety than ordinary scandate cathode.
► Stable Eu-compound could not liberate free Eu during the activation period.
► Eu2O3 had a certain diffusivity whereas Sc2O3 had poor diffusion capability.