Effect of scandia doping method on the emission uniformity of scandate cathode with Sc{sub 2}O{sub 3}–W matrix

Graphical abstract: Emission uniformity of the cathodes prepared by mechanical mixing (a) and spray drying method (b). - Highlights: • The emission uniformity of scandate cathodes has been quantitively obtained. • The nanoparticles on the cathode surface lead to the electric field enhancement. • The cathode prepared by spray drying method exhibits good emission uniformity. - Abstract: Scandia doped tungsten matrix dispenser cathodes were manufactured using scandia doped tungsten powder prepared by mechanical mixing, liquid–solid doping and a spray drying method. It is found the macrostructure of the cathode depended on the powder preparation method. The cathode prepared using the powder prepared by spray drying method had a homogenous and porous matrix characterized with grains with a diameter of less than 1 μm and with many nanoparticles distributing uniformly around these grains. The cathode with submicron structure and uniform distribution of scandia exhibited good emission uniformity. The emission uniformity ΔJ/J of the cathode prepared by spray drying method was 0.17, about 6 times lower than that of the cathode prepared by mechanical mixing method. The calculation results showed that the nanoparticles led to electric field enhancement. A Ba–Sc–O multilayer on the cathode surface and nanoparticles distributing mainly on W grainsmore » contributed to the emission property of the cathode.« less