采用液相共沉淀法和固相合成法分别制备411(4BaO:CaO:Al2O3)铝酸盐前驱粉末, 在钨网氢气炉中高温烧结. 采用喷雾干燥法结合两步氢气还原法制备出亚微米氧化钪掺杂钨粉. 随后经过压制, 烧结, 浸渍, 水洗, 退火等工艺获得具有亚微米结构的含钪扩散阴极, 并研究含钪扩散阴极的电子发射性能. 实验结果表明, 液相共沉淀法制备的铝酸盐在1500℃烧结后, 铝酸盐中Ba5CaAl4O12衍射峰最强, 结晶程度最高. 液相共沉淀法含钪扩散阴极, 脉冲发射电流密度在850℃达到37.89 A/cm2. 在激活过程中, 阴极表面形成“Ba-Sc-O”发射活性层, “Ba-Sc-O”发射活性层存在提高了阴极热电子发射能力, 降低了含钪扩散阴极的蒸发速率.
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 prepared 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/cm2 at 850℃.
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