Grain Boundary Atomic Structure and Microstructure of Bi-Sr-Ca-Cu-O, (Ti,Pb)-Sr-Ca-Cu-O and Pb-Sr-R (Rare Earth)-Ca-Cu-O Bulk Oxide Superconductors

Abstract

Electron diffraction, high resolution electron microscopy and STEM microanalysis have been carried out on bulk superconducting oxides of Bi-Sr-Ca-Cu-O, and on the new (TI,Pb)- Sr-Ca-Cu-O and Pb-Sr-R (rare earth)-Ca-Cu-O systems to elucidate microstructure and microchemistry. Real space imaging and microchemical analysis are virtually essential to provide information about the atomic structure of interfaces and other local defect structures as well as local chemical composition in the materials since microstructure controlscritical current parameter J c . The HREM images have been interpreted where necessary using the multislice image simulations with 256 x 256 Fourier transform arrays. Superstructure modulations of the type present in Bi-based and TI-Ba-Ca-Cu based compounds are not observed with the Pb substituted thallium compounds examined and it seems likely that Pb substitution stabilizes the compositions.