Characterization and superconducting properties of phases in the Bi-Sr-Cu-O system
- Oak Ridge National Laboratory, Solid State Division, Oak Ridge, Tennessee 37831-6056 (US)
Phase formation in the system Bi-Sr-Cu-O has been examined as a function of composition, temperature, ambient atmosphere, cooling history, and annealing time. Ceramic processing and melt crystallization techniques were used. For the ceramic materials (using Bi{sub 2}O{sub 3}, SrCO{sub 3}, and CuO) processed at 700{degree}C in air the Bi{sub 2}Sr{sub 2}O{sub 6} composition (221) crystallizes to a mixture of CuO, SrCO{sub 3}, and the rhombohedral Bi{sub 2}O{sub 3}. {ital x}SrO solid solution. At 800--830{degree}C in air for short durations (5 min to 2 h) the reacted products consist principally of the ideal 221 phase with minor amounts of CuO. For longer reaction times (2--400 h) the reacted products consist of the ideal 221-type structure with {ital c}=24.64 A and {ital a}=3.804 A, a collapsed'' 221 structure with {ital c}=23.6 A, and CuO. With increasing reaction time the collapsed'' 221 phase grows gradually at the expense of the ideal 221 phase. The collapsed'' 221 phase is not an oxycarbonate and appears to be a distinct ternary compound near the 221 composition, with a layered structure having a 1 A smaller stacking repeat. The ideal 221 phase is a solid solution with variable Sr content. With decreasing Sr in the starting mixture (2 to 1.25 atoms per formula unit (afu)) we observe the following: (1) the formation of the collapsed'' 21 structure is inhibited; (2) for the ideal 221 phase of {ital c}-cell dimension decrease significantly (0.2 A) and the {ital a}-cell dimension increases slightly (0.02 A); (3) the low temperature resistivity behavior changes from superconducting with {ital T}{sub {ital c}} onset of 6 K for Sr{gt}1.5 afu to semiconducting for Sr{le}1.5 afu; (4) the positions of the superlattice peaks around the (001) reflections become more incommensurate with respect to the parent structure.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5575520
- Journal Information:
- Journal of Materials Research; (USA), Journal Name: Journal of Materials Research; (USA) Vol. 4:4; ISSN JMREE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
ANNEALING
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM ADDITIONS
CALCIUM ALLOYS
CHALCOGENIDES
CHEMICAL COMPOSITION
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DOPING
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HEAT TREATMENTS
LANTHANUM ADDITIONS
LANTHANUM ALLOYS
LOW TEMPERATURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POWDERS
RARE EARTH ADDITIONS
RARE EARTH ALLOYS
SCATTERING
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
SYNTHESIS
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
X-RAY DIFFRACTION
YTTRIUM ADDITIONS
YTTRIUM ALLOYS