铁电阴极强电子发射特性和机制研究

项目名称： 铁电阴极强电子发射特性和机制研究

项目编号： No.10875095

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 冯玉军

作者单位： 西安交通大学

项目金额： 30万元

中文摘要： 铁电阴极具有强的电子发射能力，在强流电子枪、高功率微波管和高密度等离子体源等领域有重要应用前景。本项目重点研究了阴极材料、脉冲激发电场和直流抽取电压等条件对铁电阴极电子发射性能的影响，研究了铁电阴极强电子发射的物理机制。观测了正常铁电体、弛豫型铁电体、顺电体和反铁电体等各种阴极材料的电子发射现象。 研究结果表明：铁电阴极的发射电流强度与铁电材料的极化强度反转没有必然联系，而是与阴极材料的介电系数存在正相关性。在一定的脉冲电场激励下，高介电系数的陶瓷材料（如：铁电体、顺电体和反铁电体材料）都可以发射出安培级以上的电子流。在考察阴极材料的介电性能时，应该用高场中微分介电系数表征材料的介电极化性能以免出现错误。阴极发射电子流强度随着抽取电压的增加而增大。在0-5kV直流抽取电压范围内，发射电流随抽取电压线性增加没有出现饱和现象。 铁电阴极的强电子发射现象可以用"三接点"场增强理论给与解释。由于铁电材料具有高介电系数，在铁电陶瓷、金属电极和真空三种介质交汇的"三接点"处电场强度异常增大，产生场发射电子流。具有高动能的电子与周围气体和陶瓷碰撞，形成高浓度等离子体，进一步增加了电子流密度。

中文关键词： 铁电阴极；电子发射；阴极材料；介电系数；发射机制

英文摘要： Ferroelectric cathode has the capacity of emitting strong electron current, which were applied in the fields of strong electron gun, high power microwave tube and density plasma source. This project foncuses on the effects of cathode materials, pulse electric field excitation， direction voltage extraction on the electron emission properties, and the emission mechanism of ferroelectric cathode. The electron emission characteristics of ferroelectric cathode that produced by normal ferroelectrics, relax ferroelectrics, paraelectrics and antiferroelctrics were observed. The results of the study indicate that electron emission was not related to the polarization switching but related to the permittivity of cathode materials, such as paraelectrics and antiferroelectrics. Although there was no polarization switching, the cathode materials of high permittivity can still emit strong electron current under the eough pulse electric field exicitation. The permittivity of cathode materials should be remarked by the differential permittivity under strong electric field, because the permittivity is non-linear along with electric field increasing in high dielectric materials. Extraction voltage determines the electron current of cathode. The electron current is liner increasing along with extraction voltage, at the experiments of 0-5kV voltage range. The strong electron emission of ferroelectric cathode can be explained by "triple point" theory. Because cathode materials have high permittivity, at the "triple points" among cathode materials, metal electrode and vacuum, the electric field extremly enlarge which results in field emission electron. The emitted electrons collide with molecules in vacuum and cathode, thus the dense plasma is formed on cathode's surface, and makes further enhancement on electron currnet.

英文关键词： Ferroelectric cathode; Electron emission; Cathode materials; dielectric properties;Emission mechansim.