The 1212 superconductive lead cuprates: HREM study

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1993.1160· OSTI ID:5841957

Hervieu, M; Rouillon, T; Caignaert, V; Raveau, B ^[1]

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1. ISMRA-Universite de Caen (France)

The 1212 lead cuprates, Pb[sub 0.5]Sr[sub 2.5]Ca[sub 0.5]Y[sub 0.5]Cu[sub 2]O[sub 7[minus][delta]] (superconductor) and Pb[sub 0.7]Cu[sub 0.3]Sr[sub 2]Ca[sub 0.15]Y[sub 0.85]Cu[sub 2]O[sub 7[minus][delta]] (nonsuperconductor), have been examined by electron microscopy. The E.D. patterns of both oxides are characterized by the existence of extra reflections, either incommensurate satellites or superstructures. The nature of the satellites is different in the two compounds. The HREM investigations of these phases show that the satellites observed in the E.D. patterns are mainly due to local order-disorder phenomena. For Pb[sub 0.5]Sr[sub 2.5]Ca[sub 0.5]Y[sub 0.5]Cu[sub 2]O[sub 7[minus][delta]], very large areas of the crystals exhibit a highly regular contrast; besides the regular distribution of the atoms, this phase shows very rare stacking faults, which have been interpreted, and modulated zones corresponding to a local ordering of the atoms of the perovskite layers. Finally one also observes, for this oxide, local superstructures corresponding to a modulation appearing in the (111) plane of the rock salt layer and interpreted as a local ordering of lead, oxygen, and vacancies. On the opposite, the contrast of the nonsuperconducting phase, Pb[sub 0.7]Cu[sub 0.3]Sr[sub 2]Y[sub 0.85]Ca[sub 0.15]Cu[sub 2]O[sub 7[minus][delta]], is too disturbed to be interpreted, the most frequent features being the speckled aspect of the crystals. These observations support the inhomogeneous character of the superconducting transition of the 1212 lead cuprates. 21 refs., 20 figs.

• OSTI ID: 5841957
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 104:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
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CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CUPRATES
ELECTRON MICROSCOPY
LEAD COMPOUNDS
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MILLER INDICES
OXIDES
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PEROVSKITES
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STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
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