High-temperature x-ray diffraction studies of a precursor mixture for Pb-substituted Bi-2223 superconducting wires
- Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland20899 (United States)
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico87545 (United States)
High-temperature x-ray diffraction measurements of a (Bi, Pb)-2223 precursor mixture used to produce high-J{sub c} superconducting tapes were conducted on silver and ZrO{sub 2} substrates. The precursor mixture consisted primarily of 2212, Ca{sub 2}PbO{sub 4}, and CuO. Phase evolution was markedly sensitive to oxygen partial pressure: In 10{percent} O{sub 2} growth of the 2223 phase on silver was rapid, proceeded at the expense of the 2212 phase, and was preceded by the disappearance of the Ca{sub 2}PbO{sub 4} phase. When slowly heated on a silver substrate in 7.5{percent} O{sub 2} the 2212 phase melted near 800{degree}C and subsequently recrystallized near 820{degree}C in a highly textured form, but with no detectable 2223 formation. Under similar conditions on a ZrO{sub 2} substrate, the mixture exhibited no marked changes in the XRD patterns up to 850{degree}C. The dramatic reactivity on silver was also highly dependent on heating rate; rapid heating in 7.5{percent} O{sub 2} to 825{degree}C did not result in melting of the 2212 phase or appearance of the 2223 phase. In experiments leading to formation of 2223, the c-lattice parameter of the 2212 phase contracted just prior to the onset of formation of 2223. This result is consistent with the formation of an intermediate Pb-doped phase of 2212. A transient amorphous phase appeared briefly at the onset of formation of 2223. No evidence for intergrowth conversion of 2212 to 2223 was observed. {copyright} {ital 1998 Materials Research Society.}
- OSTI ID:
- 627751
- Journal Information:
- Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 3 Vol. 13; ISSN JMREEE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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