A Study of Scandia-Doped Pressed Cathodes

Scandia (Sc)-doped pressed cathodes were prepared by different methods, including mixing of scandium oxide and barium-calcium aluminates with tungsten by manual mechanical mixing, high-energy ball-milling, and liquid-liquid doping. The surface behavior of the active substance, microstructure, and emission properties of the cathodes has been studied by auger electron spectroscopy, scanning electron microscope, and an emission test apparatus. Results show that the cathodes prepared by the liquid-liquid doping method have a fine microstructure. This kind of cathode has a submicrometer semispherical tungsten grain structure with homogeneous distribution of Sc and barium-calcium aluminates which are dispersed over and among tungsten grains. The cathodes prepared by the liquid-liquid doping method exhibited good emission properties, e.g., the current density of this cathode reached 46 A/cm² at 850 ^degCb.