线性低密度聚乙烯中空间电荷陷阱的能量分布与空间分布的关系

使用激光感应压力波法和热刺激放电技术，系统地研究了直流高压作用下线性低密度聚乙烯(LLDPE)半导性电极试样中空间电荷的形成和演变及电荷陷阱分布和退极化过程.在直流高压作用下试样中空间电荷的分布明显地表现为两电极同极性电荷快速对称注入的特征，半导性电极与LLDPE的界面近乎呈现欧姆接触特征.LLDPE中的电荷陷阱分布表现出体内为浅陷阱、表层为深陷阱的特征.半导性电极与LLDPE薄片间的压合条件或电极材料对LLDPE表层的掺杂显著地影响表层陷阱的能量分布，导致表层中较深陷阱的深度和密度减小、较浅陷阱的密度增大.在整个短路退极化过程中，试样中正、负电荷的中心分别向距它们较近的电极迁移，而在开路退极后期则表现为与短路时不同的行为、被表层深陷阱再俘获的电荷脱阱后向背电极迁移. 关键词： 线性低密度聚乙烯 空间电荷 陷阱分布 热刺激放电

The relationship between energy distribution and space distribution of charge traps in linear low density polyethylene

Space charge formation and evolution, charge trap distribution, and depolarization process in linear low density polyethylene (LLDPE) samples with semiconducting electrodes subjected to dc electric stress were systematically studied using the techniques of laser induced pressure pulse and thermally stimulated discharge. Space charge distribution and evolution in the samples showed obviously the characteristics of rapid and symmetrical injection of homo-charges from the two electrodes. The interface between the semiconducting electrode and LLDPE showed approximately ohmic contact properties. The charge trap distribution in LLDPE was characterized by shallow bulk traps and deep surface layer traps. Hot-pressing conditions between the semiconducting electrode and LLDPE or contamination of the surface layer of LLDPE by the semiconducting electrode material has a remarkable effect on energy distribution of the surface layer traps, resulting in depth and density decrease of the deeper traps and density increase of the shallower traps in the surface layer. During the whole short-circuit depolarization process, the centers of positive charges and negative charges in the sample shifted to their nearer electrodes, respectively, whereas behaviors different from the short-circuit depolarization were seen in the later stage of the open-circuit depolarization, that is, the positive charges captured in the deep surface layer traps were detrapped and shifted to the rearer electrode.