Second-Generation HTS Conductors

Second-Generation HTS Conductors

Description

Thediscoveryofhightemperaturesuperconductors(HTS)in 1986bytwoIBM scientists led to an unprecedented explosion of research and development efforts world-wide because of the signi?cant potential for practical applications offered by these materials. However, the early euphoria created by the exciting prospects was dampenedby the dauntingtask of fabricating these materials into useful forms with acceptablesuperconductingproperties. Progresstowardsthisgoalhasbeen hindered by many intrinsic materials problems, such as weak-links, ?ux-creep, and poor - chanicalproperties. TheearlieststudiesofcriticalcurrentdensityJ inHTSmaterialsrevealedthatfor c apolycrystallinematerialcontainingadistributionofgrainboundariesismuchlower than that for a single crystal. High angle grain boundariesact as Josephson coupled weak-links leading to a signi?cant ?eld-dependent suppression of the supercurrent acrosstheboundary. Forcleanstoichiometricboundaries,thegrainboundarycritical currentdensity dependsprimarilyonthe grainboundarymisorientation. The dep- denceof J (gb)onmisorientationanglehasbeendeterminedYBa O Cu (YBCO) c 2 3 7?? in boundary types which can be formed in epitaxial ?lms on bicrystal substrates.
Theseinclude[001]tilt,[100]tilt,and[100]twistboundaries. Ineachcasehighangle boundarieswerefoundtobeweak-linked. Theseexperimentshavealsobeenextended to arti?cially fabricated [001] tilt bicrystals in Tl Ba CaCu O,Tl Ba Ca Cu O , 2 2 2 8 2 2 2 3 x TlBa Ca Cu O (Tl-1223) and Nd Ce CuO . In each case it was found that, 2 2 3 x 1. 85 0. 15 4 as in YBCO, J depends strongly on grain boundary misorientation angle. Data on c currenttransmissionacrossarti?ciallyfabricatedgrainboundariesinBi-2212also- dicate that most large angle [001] tilt and [001] twist boundaries are weak links. It is likely that the variation in J with grain boundary misorientation is similar in all c high-T superconductors. Hence,thelow J observedinrandomlyorientedpolycr- c c tallineHTScanbeunderstoodonthebasisthatthepopulationoflowangleboundaries issmallandthatfrequenthighangleboundariesimpedelong-rangecurrent?ow. - ingconventionalprocessingtechniques,threeHTSmaterialsweresuccessfullyfab- catedinpolycrystallineformwithmodestJ 's. ThesearetheBi-2223powder-in-tube c conductors,theTl-1223spray-pyrolyzed?lmsandtheBi-2212melt-processedthick ?lms.
Thesethreetypesofconductorscomprisedthe First-GenerationHTScond- torsorwires.


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Available Format

Details

Author(s)
Amit Goyal
Format
Hardback | 347 pages
Dimensions
155 x 235 x 20.57mm | 1,530g
Publication date
16 Dec 2004
Publisher
Springer-Verlag New York Inc.
Publication City/Country
New York, NY, United States
Language
English
Edition Statement
2005 ed.
Illustrations note
XVIII, 347 p.
ISBN10
1402081170
ISBN13
9781402081170