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  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.
Journal of Materials Research
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