High current density Sc2O3-W matrix dispenser cathode

Sciece China. Information Sciences (Impact Factor: 0.85). 01/2011; 55(1). DOI: 10.1007/s11432-011-4518-y
Source: DBLP


Sc2O3-W matrix dispenser cathodes have been prepared by powder metallurgy method and tested in Pierce electron guns. The emission current density can reach 72 A/cm2 at 900°C and over 100 A/cm2 can be achieved at a temperature higher than 950°C. The emission improves and then keeps stable with time throughout the life testing period of 330 h at a continuous loading of 88 A/cm2 pulsed current density with a pulse width of 10 μs and duty cycle of 0.2%. The cathode surface is covered by a semiconductor multilayer composed of Ba, Sc and O. The emission behavior of the cathode can be explained by a semiconductor model.

1 Follower
18 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: The microstructure of a fully activated scandia doped dispenser (SDD) cathode has been studied by scanning electron microscope (SEM). The observation results display that nanoparticles appear at the growth steps and the surface of tungsten grains of the fully activated SDD cathode. To study the influence of the nanoparticles on the emission, the local electric field strengths around the nanoparticles have been calculated by Maxwell 2D code and Comsol. The calculation results show that the local electric field strengths are enhanced by 1.1 to 3.8 times to average value based on different model conditions. The highest field strength is about 1.54 × 105 V/cm at an average field strength of 40 KV/cm, which is related to a space-charge limited (SCL) current density of 100 A/cm2 in the experimental configuration. This implies the field strength is not high enough to cause field emission.
    Functional Materials Letters 08/2013; 6(4):50040-. DOI:10.1142/S1793604713500409 · 1.61 Impact Factor
  • [Show abstract] [Hide abstract]
    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 grains contributed to the emission property of the cathode.
    Materials Research Bulletin 09/2013; 48(9):3594–3600. DOI:10.1016/j.materresbull.2013.05.069 · 2.29 Impact Factor
  • [Show abstract] [Hide abstract]
    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 degrees C. The W-Sc2O3 targets have the average grain size of about 1 pm. 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/cm(2) of idly 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.
    Materials Research Bulletin 12/2013; 48(12):5040-5044. DOI:10.1016/j.materresbull.2013.05.018 · 2.29 Impact Factor