【作者】 陈忠道；

【导师】 张树人；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2005， 博士

【摘要】 铁电阴极材料是一种在脉冲电压或脉冲激光激励下从铁电材料表面获得脉冲强流电子发射的新型功能材料。目前,它作为一种极有前途的阴极材料,已引起各国科学家的高度重视。本文主要就:1) 铁电阴极材料的制备;2) 电子发射测试系统的搭建;3) 电子发射试验的开展;4) 发射结果及机理的分析;5) 铁电阴极材料器件化的尝试等五个方面详细论述铁电阴极试验研究中取得的最新成果及经验。我们扩展了铁电阴极材料研究体系并建立了高效而可靠的测试系统,从而掌握了铁电阴极试验研究的核心技术;通过精细的微观及显微结构分析,结合材料极化特性的变化,从对比分析材料电子发射波形入手,对铁电阴极的电子发射特性及机理做出规律性的理论分析,得到具有自主技术特征的研究结果;在此基础上,进行了铁电真空二极管的试制,为铁电阴极的开发应用奠定了坚实的基础。论文研究主要内容如下: 1.在已有锆钛酸铅（PZT）材料研究基础上,着重对锆钛酸铅（PZT）、钛酸钡（BT）和钛酸铋钠（BNBT）这三个材料体系进行了深入系统研究。针对不同材料制作工艺、不同极化条件和不同发射试验条件下铁电阴极的电子发射性能,研究了发射性能与介电性能、压电性、铁电性和微观结构之间存在的关系。其中,对BT、BNBT两种环保无铅铁电材料电子发射性能的详细研究,并公开报道了其最大发射电流密度分别为30A/cm²、20A/cm²,这在国际上尚属首次。这对于扩展铁电材料研究体系,推动铁电材料的无铅化研究,具有启迪意义。 2.建立和改进高效率的电子发射电流密度测试系统,为理论分析和材料设计提供可靠的实验数据。从分析电磁干扰产生的来源机理出发,采用接地、屏蔽、线路匹配以及其他手段,有效地降低高压脉冲电子发射试验时,外界对电子发射信号的干扰强度,确保了试验工作的顺利开展。 3.研究了不同材料、不同结构的铁电阴极在不同激励电压脉冲作用下,能够达到的电子发射电流密度,对其束发射度和束亮度等发射稳定性进行了计算分析。通过试验数据的对比、归纳,优化铁电阴极的结构设计,确定铁电阴极的组分和电学参数与发射性能的匹配关系,获取最大的电流发射密度。尤其是采用硅橡胶作绝缘保护层,解决了样品击穿阈值过低的难题,提高了电子发射电流密度。 4.首次研究了铁电阴极陶瓷材料的压电参数与电子发射试验之间的关系,发现了压电系数d₃₃在电子发射过程中呈现的带有普遍意义的变化规律,并对相关机制做了解释。同时,也研究了试验条件对电子发射的影响。 5.研究了铁电电子发射机理,提出了新的观点。从电子发射波形分析入手,更多还原

【Abstract】 Ferroelectric cathode is one of the novel materials from which electrons can be emitted when voltage or laser pulse is applied on it. Now scientists from many countries pay much attention to it because of its boundless prospects. In this article, five primary research works are included: 1) the preparation of the ferroelectric samples; 2) the establishment of the testing electronic circuit for the ferroelectric electron emission; 3) the experiment of the electron emission; 4) the analyses of the ferroelectric electron emission mechanism; and 5) the preparation of the ferroelectric vacuum diode. In this article, the compositions of ferroelectric cathodes have been studied systematically. Also, the efficiency testing electronic circuit for the electron emission of ferroelectric cathode materials has been established and improved. Therefore, the kernel of experiment on ferroelectric cathode materials has been found by us. The microstructure results have been obtained and the polarization change has been observed. By analyzing the electron emission waveforms, the natural parameters of the ferroelectric electron emission and the theory of the electron emission have been generalized. Based on all these self-determination research results, the ferroelectric vacuum diode has been fabricated on trial. The main detailed work of this article is as follows:1. Based on the study of the lead zirconate titanate (PZT) ferroelectric ceramics, the barium titanate (BT) and bismuth natrium titanate (BNBT) ferroelectric materials have been systematically investigated. Using the samples with different ceramic preparation methods or different polarization factors on the different test conditions, the relationships among the electron emission, material characteristics (dielectricity, piezoelectricity, ferroelectricity, etc.) and the microstructure have been studied. Thereinto, the experiment of electron emission has been carried out for the lead-free ferroelectric ceramics BT and BNBT, and the high current density (about 30A/cm2 and 20A/cm2) is reported in the world for the first time. All these work will play enlightening role for the study of lead-free ferroelectric materials.2. The efficiency testing electronic circuit for the electron emission of ferroelectric cathode materials has been established and improved. We start this work by analyzing the origin of the electromagnetic interference (EMI), and then the jamming intensity of EMI is reduced by grounding, screening, and other methods. All更多还原