Fabrication of Aluminate for Scandia Doped Dispenser Cathode and Emission Property

Abstract

Barium calcium aluminate (4BaO:CaO:Al2O3) was synthesized via liquid phase co-precipitation and solid phase mixing respectively and sintered in hydrogen atmosphere. Scandia doped tungsten powders were pre- pared in a new process of spray drying combined with two-step hydrogen reduction. During the preparation of scandia doped impregnated cathodes, a series of procedures, including pressing, sintering, impregnating, water cleaning and annealing were taken to obtain the impregnated cathodes. The results show that Ba5CaAl4O12 is formed after high temperature sintering. After impregnation, scandia doped impregnated cathodes with porous sub-micron structure are obtained. For full activation at 1150℃, the cathode surface is covered by a Ba-Sc-O active substance layer with a preferable atomic ratio, leading to its good emission property with space charge limited current density of 37.89 A/cm 2 at 850℃.