Critical role of phase transformation during processing of Ag/Bi : 2223 tapes

Citation
Sx. Dou et al., Critical role of phase transformation during processing of Ag/Bi : 2223 tapes, IEEE APPL S, 9(2), 1999, pp. 2436-2439
Citations number
14
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
ISSN journal
10518223 → ACNP
Volume
9
Issue
2
Year of publication
1999
Part
2
Pages
2436 - 2439
Database
ISI
SICI code
1051-8223(199906)9:2<2436:CROPTD>2.0.ZU;2-O
Abstract
Phase transformation during the final stage of Ag/2223 tape processing has been investigated through quenching and normal cooling in a specially-desig ned two-step sintering process. It was found that the phase assemblage in t he final tape was determined by the equilibrium composition at the sinterin g temperature and also from any phase transformation which occurred on cool ing. A two-stage sintering procedure in the final thermal cycle was found t o be effective in transforming the liquid (or amorphous phase) and residual 2201 into 2212 and 2223. However, the annealing temperature during the fin al step was critical to the final phase assemblage. The optimal annealing t emperature of the second step in the two-step process was around 825 degree s C, where all the low T-c phases and impurities were at a minimum. Anneali ng at temperatures below 810 degrees C, resulted in a substantial increase in 3221, and a lower J(c). Annealing above 825 degrees C led to a large 221 2 fraction with a small amount of 2201 because of insufficient time needed to convert these phases into 2223 on normal cooling.