Scandium Tungsten Cathode

Hot cathode is widely used in civil, medical and military fields.

The diffusion cathode with scandium has the highest emission level, and it is the only cathode in hot cathode which can reach the current density of high power submillimeter wave device.

The emission of scandium diffusion cathode is uneven, which shows that the emission characteristics of space charge region are larger than the 3/2 power law, that is, an abnormal Schottky effect is presented. Based on the tungsten powder doped with scandium oxide, the tungsten salt was prepared by mixing the emitting salt with the doped tungsten powder, and then the tungsten based pressed cathode was prepared by powder metallurgy method. 

Prepare scandium oxide doped tungsten powder by sol gel and hydrogen reduction method, scandium oxide doped tungsten powder was mixed with 411 barium aluminate salt. After sintering, the pores were sintered in hydrogen atmosphere to obtain the porosity at 20%-25% cathode, and the emission performance was tested on the special electron emission performance tester. 

The surface morphology and energy spectrum analysis of the sintered samples were carried out, it is found that the grain size of the cathode is less than 1 microns, and the cathode has a submicron structure. There are many tetragonal crystals on the cathode surface. The tungsten grains are connected with each other. The crystal material mainly contains three elements, Sc, O and W. Active SC plays a decisive role in the cathode activation process, which also indicates that the cathode obtained by Sc₂WO₃O₁₂ has better activity and can effectively improve the emission performance of cathode.

The addition of tungsten powder promotes the activation of the active element Sc in the cathode, which is beneficial to the reaction between the emission salt and the matrix element tungsten. During the activation process, the active element Sc diffused from the cathode to the surface and formed a uniform distribution of Sc, O and W active layers on the surface. The emission performance of the active element was 4 times of that of the barium tungsten cathode.

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