Effects of oxygen annealing on 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 to 925/sup 0/C in air were pressed at 35 MPa into bars, sintered at 950/sup 0/C in air for six hours, and slow-cooled at 50/sup 0/C/h to room temperature. The effects of subsequent oxidation processing on superconducting properties were investigated in the study reported here. 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 90/sup 0/K with a 2-degree transition width. High-pressure oxidation (2000 psi O/sub 2/) at 200/sup 0/C for one week of a sample previously optimized at 450/sup 0/C significantly decreased the volume fraction of superconducting material, but did not affect the transition temperature. Results based on iodometric titration measurements and thermogravimetric analysis suggest that under optimum conditions the copper valency is about 2.3 and oxygen stoichiometry is 6.94 (x = 0.06). 4 figs.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5613779
- Report Number(s):
- PNL-SA-15183; CONF-870878-4; ON: DE88005687
- Resource Relation:
- Conference: Conference on atomic and molecular processing of electronic and ceramic materials: preparation, characterization and properties, Seattle, WA, USA, 31 Aug 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Influence of oxygen variation on the crystal structure and phase composition of the superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/
Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
OXIDATION
SUPERCONDUCTIVITY
COPPER OXIDES
YTTRIUM OXIDES
ANNEALING
HIGH PRESSURE
OXYGEN
STOICHIOMETRY
TRANSITION TEMPERATURE
VALENCE
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COPPER COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
HEAT TREATMENTS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity