Structural and chemical disorder near the Y[sub 2]BaCuO[sub 5]/YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] interface and its possible relation to the flux-pinning behavior in melt-textured
- Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)
Transmission-electron microscopy and energy-dispersive x-ray spectroscopy were used to study the microstructure of the YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] (1:2:3) region adjacent to the Y[sub 2]BaCuO[sub 5]/YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] (2:1:1/1:2:3) interface. It is found that there exists a high local density of stacking faults in 1:2:3, near the 2:1:1/1:2:3 interfaces. The stacking faults lie parallel to the (001) basal plane and are inhomogeneously distributed around the 2:1:1 particles. They tend to be disk shaped with diameters ranging from a few to [similar to]30 nm. Calculations made using simple energy considerations suggest that these stacking faults may act as effective flux pinners for magnetic fields directed both parallel and perpendicular to the basal plane. They may account for the observed increase of [ital J][sub [ital c]] with volume fraction of 2:1:1 and also explain the angular dependence of transport [ital J][sub [ital c]] in melt-processed 1:2:3. An unusual tendency for the formation of facets on the incoherent, randomly oriented 2:1:1 particles parallel to the [l brace]001[r brace]-type planes in the 1:2:3 matrix was also observed. Microanalysis of the 1:2:3 region around the 2:1:1 particles, which contain few or no stacking faults, consistently shows an enrichment of Y and a corresponding depletion in Ba concentration. Such cation nonstoichiometry may result in the formation of numerous point defects, which could also result in pinning. The presence of ledges on some facets at the 2:1:1/1:2:3 interfaces and the observed compositional nonstoichiometry in the 1:2:3 phase in the vicinity of these interfaces suggest that 2:1:1 particles continue to change in size after entrapment in 1:2:3. The observed compositional variation is consistent with dissolution of trapped 2:1:1.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6671344
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 47:9; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HIGH-TC SUPERCONDUCTORS
MICROSTRUCTURE
BARIUM OXIDES
CHEMICAL COMPOSITION
COPPER OXIDES
MAGNETIC FLUX
MELTING
STACKING FAULTS
TEXTURE
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTROSCOPY
YTTRIUM OXIDES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SPECTROSCOPY
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)