Scandia Effect Tungsten Oxide Powder Reduction Process

Vacuum electronic devices have a wide application in civil and military fields such as communication, radar and industrial heating. Cathode is an important component in the device since it provides the required electronic beam for the device. Among all the electron emitters, scandate cathodes have aroused great attention among all the cathodes due to their copious emission property.

Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten powder, powder morphology and doped tungsten matrix were characterized by scanning electron microscope, X-ray diffraction and laser diffraction particle size analyzer, respectively. The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 on the property of tungsten powder were studied by the temperature programmed reduction. The experimental results showed that the precursor powders prepared by spray drying had spherical shape. The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide. The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder. By using this kind powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium were obtained.

The addition of Sc2O3 shifted the hydrogen consumption peak to the lower temperature side. Namely, the reduction temperature of tungsten oxide decreased with Sc2O3 addition. Adding scandia could decrease the particle size of tungsten. The scandia doped tungsten powder prepared by spray drying method had sub-micrometer size in the range of 0.1μm to1μm in semispherical shape and scandium distributed evenly in the powder. Using scandia doped tungsten powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium was obtained.

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