scholarly journals Texture Investigations on High Temperature Superconductors

1995 ◽  
Vol 24 (1-3) ◽  
pp. 93-103 ◽  
Author(s):  
Dietrich Schläfer ◽  
Klaus Fischer ◽  
Margitta Schubert ◽  
Brigitte Schlobach
Keyword(s):  
High Temperature ◽  
High Temperature Superconductors ◽  
Rotation Symmetry ◽  
Pole Figures ◽  
Composite Conductors ◽  
Current Densities ◽  
Powder In Tube ◽  
Thick Layers ◽  
Lotgering Factor

The formation of a structure with strong crystallographic texture is an important requirement for high critical current densities at 77 K in high temperature superconductive materials (HTSC). In this work several methods for texture investigation in the superconductive phase of BiPbSrCaCuO/Ag- and YBaCuO/AgPd-composite conductors prepared according to the “powder in tube”-method as well as in YBaCuO-thick layers are presented. For the characterisation of the texture development in dependence on technological steps at the preparation of HTSC-composite conductors the determination of the halfwidth FWHM from the psi-scan or for one-phase specimens the determination of the Lotgering-factor is appropriate, if only a c-axis exists. The measurement of pole figures is necessary to determine, whether a rotation symmetry occurs or an orientation of the (a,b)-directions exists. The use of the omega-scan to determine the half-width is not useful, if the goniometer unit is intended and optimised for phase analysis and therefore the secondary monochromator cannot be relinquished.

Important Considerations for Processing Bi-Based High-Temperature Superconducting Tapes and Films for Bulk Applications

MRS Bulletin ◽  
1992 ◽  
Vol 17 (8) ◽  
pp. 45-51 ◽  
Author(s):  
Eric E. Hellstrom
Keyword(s):  
High Temperature ◽  
Magnetic Fields ◽  
Materials Science ◽  
Weak Link ◽  
High Temperature Superconductors ◽  
Electromagnetic Properties ◽  
High Magnetic Fields ◽  
Large Current ◽  
Current Densities ◽  
Made In

High-temperature superconductors are brittle oxide ceramics, yet they have been made into wire that has been wrapped into solenoids and used in demonstration magnets and motors. Fabricating wires from these ceramics is an extremely challenging materials science process that requires a precisely engineered microstructure with the correct chemical, mechanical, and electromagnetic properties if these wires are to transport large current densities (Jc) in high magnetic fields. Heine et al. first demonstrated that wires of these materials could carry high Jc in very high magnetic fields. At 4.2 K, the oxide superconducting wires can carry higher Jc at higher magnetic fields than conventional Nb-Ti or Nb3Sn wires (Figure 1), and as shown in the companion article in this issue by Kato et al. they can also have high Jc at 77 K.Of the three major families of high-temperature superconductors, YBa2Cu3O7-x, Bi-Sr-Ca-Cu-O (BSCCO), and Tl-Ba-Ca-Cu-O, the best wires to date have been made in the BSCCO system. At present, all YBa2Cu3O7-x wires are weak linked and have only small Jc in magnetic fields. In the Tl-based system, the superconducting properties are potentially very interesting, but the toxicity of Tl and the system's complex processing have limited conductor development. For the Bi-based system, the basic processing steps are becoming known, the grains are well connected, and the weak link problem can be controlled. This permits applications in the temperature range 4–77 K, depending on the field and current density requirements of the particular use.

Determination of the Orientation Relations between the Low- and High-Temperature Phases of NiS

2010 ◽  
Vol 160 ◽  
pp. 177-182
Author(s):  
Heidrun Sowa ◽  
Helmut Klein ◽  
Lars Raue
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Imaging Plate ◽  
Transition Mechanism ◽  
Orientation Relations ◽  
Pole Figures ◽  
Main Component ◽  
Nias Type ◽  
Imaging Plate Detector

In order to get information about the transition mechanism, the temperature-induced transformation in the binary com¬pound NiS was investigated. Above 379 °C, a single crystal of millerite -NiS transforms to polycrystalline NiAs type -NiS with a sharp texture. Pole figures of both phases in the same orientation were measured using synchrotron radiation and an imaging plate detector. The Rietveld texture analysis showed that there are at least three components of the high-temperature -NiS phase. The main component shows the following orientation relations: [001]NiAs type  [001]millerite, [100]NiAs type  [210]millerite, [210]NiAs type  [100]millerite. The broad peaks of the recovered polycrystalline millerite occur at the same positions as the reflections of the original single crystal.

A New Method to Obtain U(J) Relationship in High Temperature Superconductor

1997 ◽  
Vol 11 (06) ◽  
pp. 753-765 ◽  
Author(s):  
M. J. Qin ◽  
X. Jin ◽  
X. X. Yao ◽  
Y. X. Fu ◽  
X. S. Rong ◽  
...  
Keyword(s):  
High Temperature ◽  
Magnetic Relaxation ◽  
High Temperature Superconductor ◽  
High Temperature Superconductors ◽  
Usual Method ◽  
New Method ◽  
Relaxation Data ◽  
J Curve ◽  
Different Temperatures

An implicit expression for the time dependence of the current density J(t) is derived without the constant assumption of dU/dJ or <dU/dJ>, based on which a new method to extract U(J) relationship from magnetic relaxation data in high temperature superconductors is described. This method is applied to a melt textured growth YBa2Cu3O6+x sample and we obtain U(J)~ J-μ with μ=0.90 for H‖c, which is in accordance with that derived by the usual method suggested by Malery et al.(μ=0.87). Moreover, both methods give the same value of the constant C, which implies that the determination of C by the requirement of continuity of the U(J) curve at different temperatures is reliable. And the results U(J)~ J-μ by both methods are evidence for the collective pinning or the vortex glass theory.

Determination of current and flux distribution in squares of thin-film high-temperature superconductors

1994 ◽  
Vol 229 (3-4) ◽  
pp. 289-300 ◽  
Author(s):  
P.D. Grant ◽  
M.W. Denhoff ◽  
W. Xing ◽  
P. Brown ◽  
S. Govorkov ◽  
...  
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Flux Distribution ◽  
High Temperature Superconductors
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