Solidification of Bi[sub 2]Sr[sub 2]Ca[sub 1]Cu[sub 2]O[sub [ital y]] and Bi[sub 2]Sr[sub 1. 75]Ca[sub 0. 25]CuO[sub [ital y]]
- Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)
- Ames Laboratory, Iowa State University, 214 Wilhelm, Ames, Iowa 50011 (United States)
The solidification processes for the compositions Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub [ital y]] (2212) and Bi[sub 2]Sr[sub 1.75]Ca[sub 0.25]CuO[sub [ital y]] (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. In both cases, the solidus is lowered to approximately 750 [degree]C. Solidification of Bi[sub 2]Sr[sub 1.75]Ca[sub 0.25]CuO[sub [ital y]] in Ar resulted in a divorced eutectic structure of Bi[sub 2]Sr[sub 2[minus][ital x]]Ca[sub [ital x]]O[sub [ital y]](22[ital x]) and Cu[sub 2]O while solidification of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub [ital y]] in Ar resulted in a divorced eutectic structure of Bi[sub 2]Sr[sub 3[minus][ital x]]Ca[sub [ital x]]O[sub [ital y]](23[ital x]) and Cu[sub 2]O. Solidification of Bi[sub 2]Sr[sub 1.75]Ca[sub 0.25]CuO[sub [ital y]] in O[sub 2] resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22[ital x] and CuO/Cu[sub 2]O. Solidification of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub [ital y]] in partial pressures of 1%, 20%, and 100% oxygen resulted in multiphase samples consisting of 2212, 2201, some alkaline-earth cuprates, and both divorced eutectic structures found during solidification in Ar. For both compositions, these latter structures can be attributed to oxygen deficiencies present in the melt regardless of the overpressure of oxygen. These eutectic structures are unstable and convert into the superconducting phases during subsequent anneals in oxygen. The formation process of the 2212 phase during solidification from the melt was determined to proceed through an intermediate state involving the 2201 phase.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- DOE Contract Number:
- W-31109-ENG-38; W-7405-ENG-82
- OSTI ID:
- 6097873
- Journal Information:
- Journal of Materials Research; (United States), Vol. 8:9; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BISMUTH OXIDES
EUTECTOIDS
SOLIDIFICATION
CALCIUM OXIDES
COPPER OXIDES
STRONTIUM OXIDES
OXYGEN
PARTIAL PRESSURE
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
ELEMENTS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
STRONTIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication