混合基含钪扩散阴极微观结构与性能研究

Study on Scandia Mixed Matrix Impregnated Cathode in Microstructure and Properties

为了获得发射性能优异,均匀性良好的热电子发射阴极,本文采用液-液掺杂结合两步氢还原法制备出氧化钪掺杂钨粉,并在此基础上通过压制、烧结和浸渍工艺制备出浸渍型扩散阴极。采用SEM、电子发射测量装置和AES对阴极微观结构、发射性能和激活期间阴极表面活性元素的变化进行了研究。研究结果显示:阴极孔度合适,孔结构良好,孔分布均匀,颗粒达到亚微米级。该阴极的发射测试结果显示在850℃b时Jdiv为51A.cm-2。分析认为阴极的亚微米结构有利于激活和工作过程中活性物质的扩散和在表面的均匀分布,对阴极的发射起促进作用。

In order to obtain cathodes with excellent electron emission and uniform emission properties,the Sc2O3 doped tungsten powders were prepared by sol-gel combined with two-step reduction method.By using this kind of powder,scandia doped tungsten mixed matrix impregnated cathodes were fabricated by a serial procedures of pressing,sintering and impregnating.The various analysis techniques,such as SEM,AES,and electron emission property measurement equipments were adopted to evaluate the microstructure,emission properties and the changes of active element on cathode surface during activation.The SEM micrographs show that Sc2O3 doped tungsten matrix has appropriate pore size,good pore structure,uniform pore distribution,and sub-micrometer-sized grains. 51 A·cm-2 of Jdiv.at 850 ℃b,nearly the highest thermoelectronic emission current density in the world,is obtained for this kind of impregnated cathode.It is the microstructure that is propitious to the diffusion of active element from interior to the surface,which accelerates the electron emission property of the cathode.