Effect of tungsten powder particle shape on the emission properties of the barium tungsten cathode

Abstract

In this research, porous W matrixes for dispenser Ba-W cathodes were prepared by metal injection molding (MIM) using W powders with different particle shapes as raw materials. Other than investigating the effect of the powder particle shape on the pore characteristics of the porous W matrix, the influence of the powder particle shape on the emission properties of the Ba-W cathode was also investigated. Irregular W powder particles had higher surface roughness and specific surface area than the spherical W particles, resulting in sinuous pore channels and higher pore-specific surface area in the prepared W matrix. The emission current density of the cathode processed from the irregular powder was thus improved as the level of Ba–O dipoles, covered on the emission surface, was increased. This is due to the high pore-specific surface area offering a high contact area between W and impregants in the cathode.