Investigation of Sc2O3mixed-matrix Ba—Ca aluminate-impregnated cathodes

The Sc2O3mixed-matrix Ba-Ca aluminate-impregated cathodes are fabricated and electron emission property as well as Ba evaporation rate is evaluated. The saturation current density Js= 10 A/cm²can be obtained at 840°C of brightness temperature for Sc2O3content of 1-13 wt %. Emission anomaly is observed at low applied electric field strength, which is caused by the effective electric field reduction due to patch field. From surface analysis by Auger electron spectroscopy, the patch field is found to be due to imhomogeneous distribution of a surface layer composed of Ba, Sc, and O.