Characteristics of scandate-impregnated cathodes with sub-micron scandia-doped matrices

We describe in this paper scandate-impregnated cathodes with sub-micron scandia-doped tungsten matrices having an improved uniformity of the Sc distribution. The scandia-doped tungsten powders were made by both liquid–solid doping and liquid–liquid doping methods on the basis of previous research. By improving pressing, sintering and impregnating procedures, we have obtained scandate-impregnated cathodes with a good uniformity of the Sc2O3- distribution. The porosity of the submicron structure matrix and content of impregnants inside the matrix are similar to those of conventionally impregnated cathodes. Space charge limited current densities of more than 30 A/cm2 at 850 8Cb have been obtained in a reproducible way. The current density continuously increases during the first 2000 h life test at 950 8Cb with a dc load of 2 A/cm2 and are stable for at least 3000 h.