Journal of Superconductivity, VoL 9, No. 3, 1996 Structural Modifications of the Superconducting Phases on Bi System by Electron Beam Irradiation G. Aldica, ~ I. I. Geru, 2 B. M. Puscasu, 3 F. Constantinescu, 1 and P. Badica 4 Received 25 September 1995 Superconducting samples of the Bi(Pb)-Sr-Ca-Cu-O system have been irradiated in transmis- sion electron microscopy (TEM) to investigate the effect of a relative high fluence of electrons with 75 and 100 keV energy on the microstructure of the material. The diffraction pattern images show a dramatic change from very uniform lattice spots at ab crystalline planes to a circular pattern corresponding to damage and breaking of the materials in very small crystallites. KEY WORDS: Electron irradiation; Bi-Pb Sr-Ca-Cu-O high-T,.phases; phases stability;microstructure transformations; transmission electron microscopy. 1. INTRODUCTION All high-temperature superconducting materials are subject to irradiation damage by knock-on dis- placive events and thermal dissipation under a particle beam on domains near the grain's surface. These mat- erials are very sensitive to various irradiation types (ions, electrons, neutrons, photons, etc.). The irradia- tion effects influence the electrical resistivity p, the critical temperature T~, the critical current density jc, etc. The modifications can be explained by the peak widths of the state density function [ 1 ], by the influ- ence of localization of same-sign charge carriers on repulsive Coulomb interaction [2], and by the cou- pling energy of the Cooper pair [3]. A more suitable description of these phenomena may be obtained from the chaotic phase approach, analyzing the influ- ence of charge carrier scattering on Bose-Einstein ~Institute of Physics and Technology of Materials, Bucharest-Mag- urele, P.O. Box MG-7, Romania. 2Faculty of Physics, Moldava State University, 277009 Kishinew, R. Moldova. 3Metrological and Automatization Research Center, Academy Sciences of Moldova, St. Academia, 277028 Kishinew, R. Moldova. 4Facultyof Physicsand Engineering,Department of PowderMetal- lurgy, Refractories, and Composites, Kiev Polytechnic Institute, 252056 Kiev, Ukraine. condensation of Cooper pairs [4]. In this approach, at a certain critical value of the irradiation fluence abe, a phase transition to the state within T~=0, j~=0, and p-~cc occurs. For 60 > q)~ a nonmetallic type of resistivity versus temperature dependence is observed. This fact characterizes the state's localization in the solid and shows that in the new phase the charge carriers (in our case the holes) are close to the localiza- tion state. The influence of irradiation defects on T~,j~, and p is often explained using the granular structure idea and the l intergranular boundary features within different properties given the intragranular properties, etc. All references show that the various kinds of 273 10 20 30 L,O 50 60 20 (deg ) Fig. 1. X-ray diffractionpattern of sample F. 0896-I 107/96/0600-0273509.50/0 9 ~996 Plenum Publishing Corporation