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 sub-micron 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 °Cb have been obtained in a reproducible way. The current density continuously increases during the first 2000 h life test at 950 °Cb with a dc load of 2 A/cm2 and are stable for at least 3000 h.