Concurrent Effects of Electronic and Lattia Excitations and Electric Field on Electrical Conductirity

本项目的第一个目标是建立一种在高压电子显微镜中测量电导率的方法。第二个目标是深入了解电子和晶格激发对陶瓷材料中缺陷团簇的成核和生长过程以及电导率（sigma）和介电损耗角正切（tan δ）等电性能的影响。主要研究结果如下：1.建立了在电场下用电子和离子照射期间测量电导率的方法，并证实缺陷σ和tan δ分别高于2 × 10 - 4<-5>/Ω/m和1 × 10 <-4>- 4/Ω/m。在1000 keV电子辐照下，ZrO_2-3%Y_2O_3和MgO的σ和tan δ值在300 ~ 800 K范围内增加，表现出增强效应。更系统的e4实验需要得到结论性的意见，这些电性能的辐射增强的机制。2. 1000 keV电子对30 keV He^+、Ar^+或Ar ^+离子引起的级联损伤的同时作用表现为抑制了Si和Ge中级联损伤的积累，促进了MgO-nAl_2 O_3中缺陷团簇的成核和生长。证实了电场对描述成核和生长过程以及辐照过程中电学性质的重要性。建立了一组动力学方程，描述了辐照和电场对缺陷团簇形核和生长过程的共同作用。

The first objective of the present project lies on the establishment of the method for measuring the electrical conductivity in a high voltage electron microscope. The second objective is to get insights into the concurrent effect of electronic and lattice excitation on the nucleation and growth process of defect clusters and electrical properties such as electrical conductivity(sigma) and dielectric loss tangent(tan delta) in ceramic materials. The results obtained are as follows ; 1. A method for measuring the electrical conductivity during irradiation with electrons and ions under electric field was established and was confirmed to defect sigma and tan delta higher than 2 x 10^<-5>/OMEGA/m and 1 x 10^<-4>, respectively. The values of sigma and tan delta for ZrO_2-3%Y_2O_3 and MgO increased at temperatures between 300 and 800 K under irradiation with 1000 keV electrons, showing their enhancement. More systematic e4experiments are required to get conclusive remarks on the mechanism of the irradiation enhancement of those electrical properties. 2. The concurrent effect of 1000 keVelectrons on cascade damages induced by 30 keV He^+, Ar^+ or Xe^+ ions was defected as a retardation of the accumulation of cascade damages in Si and Ge and as the enhancement of the nucleation and growth of defect clusters in MgO-nAl_2O_3.3. The importance of electric field was confirmed for describing the nucleation and growth process as well as the electrical properties during irradiation. A set of kinetic equation was established for describing the concurrent effect of irradiation and electric field on the nucleation and growth process of defect clusters.