Wang Jinshu, Zhang Xizhu, Liu Wei, Cui Yuntao, Wang Yiman, Zhou Meiling
School of Materials Science and Engineering, Beijing University of Technology, Beijing, 100124, China.
J Nanosci Nanotechnol. 2012 Aug;12(8):6499-504. doi: 10.1166/jnn.2012.5415.
RE2O3-Mo/W cathodes were prepared by powder metallurgy method. La2O3-Y2O3-Mo cermet cathodes prepared by traditional sintering method and spark plasma sintering (SPS) exhibit different secondary emission properties. The La2O3-Y2O3-Mo cermet cathode prepared by SPS method has smaller grain size and exhibits better secondary emission performance. Monte carlo calculation results indicate that the secondary electron emission way of the cathode correlates with the grain size. Decreasing the grain size can decrease the positive charging effect of RE2O3 and thus is favorable for the escaping of secondary electrons to vacuum. The Scandia doped tungsten matrix dispenser cathode with a sub-micrometer microstructure of matrix with uniformly distributed nanometer-particles of Scandia has good thermionic emission property. Over 100 A/cm2 full space charge limited current density can be obtained at 950Cb. The cathode surface is covered by a Ba-Sc-O active surface layer with nano-particles distributing mainly on growth steps of W grains, leads to the conspicuous emission property of the cathode.
采用粉末冶金法制备了RE2O3-Mo/W阴极。通过传统烧结法和放电等离子烧结（SPS）制备的La2O3-Y2O3-Mo金属陶瓷阴极表现出不同的二次发射特性。采用SPS法制备的La2O3-Y2O3-Mo金属陶瓷阴极晶粒尺寸较小，二次发射性能较好。蒙特卡罗计算结果表明，阴极的二次电子发射方式与晶粒尺寸有关。减小晶粒尺寸可以降低RE2O3的正电荷效应，从而有利于二次电子向真空逃逸。具有基体亚微米微观结构且氧化钪纳米颗粒均匀分布的氧化钪掺杂钨基扩散阴极具有良好的热电子发射性能。在950℃时可获得超过100 A/cm2的全空间电荷限制电流密度。阴极表面覆盖有Ba-Sc-O活性表面层，纳米颗粒主要分布在W晶粒的生长台阶上，导致阴极具有显著的发射性能。
