Bi-Ca-Sr-Cu-O superconductors

Conference · Wed Mar 01 04:00:00 EST 1989 · IEEE Trans. Magn.; (United States)

OSTI ID:6041420

Green, S M; Rudee, M L; Mei, Y; Luo, H L; Ramesh, R; Thomas, G

The connectivity problem in Bi-Ca-Sr-Cu-O superconductors is addressed in this paper. Bulk samples always exhibit a step in the resistivity plot, consequent to which zero resistance is obtained around 75K, although the onset is above 110K. Magnetic measurements indicate the presence of almost equal fractions of two superconducting phases with transition temperatures of 110K and about 80K. The microstructure of these samples has been examined using several transmission electron microscopy techniques. The superconducting phases exhibit a polytypoid type structure with the general formula of Bi/sub 2/Sr/sub 2/ Ca/sub n-1/Cu/sub n/O/sub y/, where n takes on values of 1,2,3 and in some infrequent cases 4. The c-parameter of T/sub c/ increase with n. In almost all the superconducting grains, the lower T/sub c/(n=1 or 2) polytypoid is observed at the grain boundaries. Thus, the 110K polytypoid in each grain is not connected to similar regions in other grains. The lower T/sub c/ polytypoid is observed at the grain boundaries due to a reduction of Ca and/or Cu. It is suggested that the controlled addition of PbO enables the formation of a Pb-rich liquid phase which makes the composition near the grain boundaries uniform. Consequently, the step in the resistivity plot disappears.

• Research Organization: 9525167; 9506418
• OSTI ID: 6041420
• Report Number(s): CONF-880812-
• Conference Information: Journal Name: IEEE Trans. Magn.; (United States) Journal Volume: 25:2
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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656100 -- Condensed Matter Physics-- Superconductivity
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRIC IMPEDANCE
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
GRAIN BOUNDARIES
IMPEDANCE
MAGNETIC FIELDS
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TRANSMISSION ELECTRON MICROSCOPY