Electron Microscopy of the Pb-Sr-Ca-Er-Cu-O Superconductor

The structure and microstructure of a solid state processed Pb-Sr-Ca-Er-Cu-O superconductor have been investigated by transmission electron microscopy. In addition to the majority superconducting phase, at least two other impurity phases have been observed. The superconducting phase is a layered structure similar to the Bi2Sr2CaCu2Cycompound, with an extra Cu atom between the two PbO layers. Stacking defects inside the grain have been observed. A grain boundary amorphous phase has also been observed. The steps in the resistivity-temperature plot and the consequent absence of Tc, 0 above 8 K are attributed to either the presence of the Pb2Sr2Cu2Oyunit cell at the grain boundary and/or a local enrichment of oxygen at the grain boundaries. Superlattice spots in the [100] zone axis diffraction patterns from regions enriched in Ca and Er with respect to the nominal composition are interpreted as due to ordering of Sr and Ca/Er in the Sr sites. © 1990, Materials Research Society. All rights reserved.