Skip to main content
OSTI.GOVU.S. Department of Energy Office of Scientific and Technical Information
U.S. Department of Energy
Office of Scientific and Technical Information
 

Bi-Ca-Sr-Cu-O superconductors: The connectivity issue

Conference ·
OSTI ID:6810375
; ; ; ; ;
The connectivity problem in Bi-Ca-Sr-Cu-O superconductors is addressed in this paper. Our 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 and 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 Ca and/or Cu. It is suggeted 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. 19 refs., 6 figs.
Research Organization:
Lawrence Berkeley Lab., CA (USA)
DOE Contract Number:
AC03-76SF00098
OSTI ID:
6810375
Report Number(s):
LBL-25842; CONF-880812-7; ON: DE89000558
Country of Publication:
United States
Language:
English

Similar Records

Bi-Ca-Sr-Cu-O superconductors
Conference · Tue Feb 28 23:00:00 EST 1989 · IEEE Trans. Magn.; (United States) · OSTI ID:6041420
Polytypoid structure of Pb-modified Bi-Ca-Sr-Cu-O superconductor
Journal Article · Sat Oct 01 00:00:00 EDT 1988 · Phys. Rev. B: Condens. Matter; (United States) · OSTI ID:6781662
Grain boundaries and defects in superconducting Bi-Sr-Ca-Cu-O ceramics
Journal Article · Sun Dec 31 23:00:00 EST 1989 · Journal of Applied Physics; (USA) · OSTI ID:7246908

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
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 DEFECTS
CRYSTAL STRUCTURE
GRAIN BOUNDARIES
MAGNETIC PROPERTIES
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POINT DEFECTS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
VACANCIES