Processing relationships in YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconductors
Samples of YBa/sub 2/Cu/sub 3/O/sub 7-x/ were prepared by solid state reaction of Y/sub 2/O/sub 3/, BaO/sub 2/, and CuO powders mixed in stoichiometric proportions. Powders reacted at 900/sup 0/C-925/sup 0/C in air were pressed at 35 MPa into rectangular bars and sintered at 950/sup 0/C in air for six hours. Slow cooling at 50/sup 0/C/hour promoted complete transformation to the orthorhombic structure. The effects of subsequent oxidation processing on superconducting properties were also investigated. Oxidation anneals at one atmosphere pressure in flowing O/sub 2/ over the temperature range from 300 to 550/sup 0/C were performed. Results indicate that oxidation at 450/sup 0/C optimized the superconducting transition temperature at 91K with a 2-degree transition width. Subsequent high-pressure oxidation (2000 psi O/sub 2/) at 200/sup 0/C for one week significantly degraded the superconducting characteristics. Results based on iodometric titration measurements and thermogravimetric analysis suggest that the copper valency is about 2.3 and oxygen stoichiometry is 6.94 (x = 0.06) in samples processed to optimize superconducting properties. 11 refs., 3 figs.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5530906
- Report Number(s):
- PNL-SA-15380; CONF-871124-58; ON: DE88005137
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society, Boston, MA, USA, 30 Nov 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
SUPERCONDUCTIVITY
COPPER OXIDES
SUPERCONDUCTORS
PROCESSING
YTTRIUM OXIDES
ANNEALING
OXIDATION
STOICHIOMETRY
TRANSITION TEMPERATURE
VALENCE
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COPPER COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HEAT TREATMENTS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity