反铁电陶瓷的强电子发射特性研究

Strong electron emission of antiferroelectric ceramic

采用掺镧锆锡钛酸铅反铁电陶瓷作为阴极材料,研究了脉冲电压激励下陶瓷的电子发射特性.当激励电压为800V、抽取电压为0V时,得到1.27A/cm2的发射电流密度;当抽取电压增加到4kV时,获得1700A/cm2的发射电流密度.分析了发射电流随抽取电压的变化关系,讨论了反铁电陶瓷强电子发射的内在机理.结果表明:掺镧锆锡钛酸铅反铁电陶瓷能够在较低的激励电压(400V)下实现电子发射,发射电流远大于按照Child-Langmuir定律计算出的电流,三接点附近局域反铁电—铁电相变产生初始电子发射,初始电子电离中性粒子形成等离子体,增强了电子发射.

The electron emission of a novel antiferroelectric cathode material La-doped Pb（Zr, Sn, Ti） O3 （PLZST） has been studied. For driving voltage of 800 V and accelerating voltage of 0 V, the emission current density was 1.27 A/cm2 . For driving voltage of 800 V and accelerating voltage of 4 kV, a strong emission current density with 1700 A/cm2 was obtained. The dependence of emission current on accelerating voltage was analyzed and the mechanism of antiferroelectric electron emission was discussed. It was found that strong electron emission from antiferroelectric material can be realized under lower driving voltage and the emission current was much larger than that predicted by the Child-Langmuir law. Local antiferroelectric-ferroelectric phase transition in the vicinity of the triple junction leads to initial electron emission, and these initial electrons then cause desorption of gas which had been absorbed at the ceramic surface. The desorbed gas is then ionized, which leads to plasma generation. The formation of surface plasma enhances the emission current.