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

本课题的第一个目标是建立在高压电子显微镜下测量电导率的方法。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性能（如电导率（sigma）和介电损耗正切（tan delta））的同时影响。所得结果如下：1. 建立了一种测量电场下电子和离子辐照时电导率的方法，证实了σ和tan δ分别高于2 × 10^<-5>/OMEGA/m和1 × 10^<-4>。ZrO_2-3%Y_2O_3和MgO在温度为300 ~ 800 K时，在1000 keV电子的照射下，σ和tan δ值有所增加，表现为增强。需要更系统的e4实验才能对辐照增强这些电学性能的机理得出结论性的结论。2. 在30 keV He^+、Ar^+或Xe^+离子引起的级联损伤中，1000个keve的同时作用是阻碍了Si和Ge中级联损伤的积累，并促进了MgO-nAl_2O_3.3中缺陷团簇的成核和生长。证实了电场对于描述辐照过程中的成核和生长过程以及电学性质的重要性。建立了一套动力学方程，描述了辐照和电场对缺陷团簇成核和生长过程的共同影响。

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.