Some data of emission and evaporation properties related to tungsten matrix structures of the impregnatedcathodes are analyzed.The results indicate that the particle size of tungsten powder and the pore size in the porousmatrix determine the total inside surface area of all pores,the diffusion length of barium atoms over tungsten grainsurfaces,and the diameter and length of the path through which barium atoms are transported.These factors allrelate to the properties and operation mechanism of an impregnated cathode;therefore,it would not be strictlycorrect to use only the matrix porosity for characterizing the cathode properties.Finally,the preferred structures ofporous tungsten matrix depending on different applications of impregnated cathodes are proposed. Some data of emission and evaporation properties related to tungsten matrix structures of the impregnated cathodes are analyzed. The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total inside surface area of ​​all pores, the diffusion length of barium atoms over tungsten grainsurfaces, and the diameter and length of the path through which barium atoms are transported.These factors allrelate to the properties and operation mechanism of an impregnated cathode; therefore, it would not be strictlycorrect to use only the matrix porosity for characterizing the cathode properties. Finaally, the preferred structures of porous tungsten matrix depending on different applications of impregnated cathodes are proposed.