Speaker
Dr
Jens Haenisch
(Karlsruhe Institute for Technology)
Description
YBa2Cu3O7-x based coated conductors have large potential in such diverse applications as wires/cables, motors/generators, high-field coils, and superconducting permanent magnets, each of them with a certain range of temperature and magnetic field and a certain need in magnitude and isotropicity in critical current density Jc. In order to use the full potential of YBa2Cu3O7-x, it is mandatory to tailor its transport properties for the envisaged application. This is done by inserting artificial pinning centers, such as perovskites (e.g. BaZrO3) or (mixed) double-perovskites, which precipitate as nanoparticles and/or nanorods.
We report on a study on the addition of the mixed double perovskite Ba2Y(Nb/Ta)O6 to YBa2Cu3O7-x thin films on SrTiO3 single crystals prepared by pulsed laser deposition. Size, shape, density and orientation distribution of these pinning centers are analysed by X-ray diffraction and TEM. The electrical transport properties are determined in 4-point geometry in maximum-Lorentz force configuration in fields up to 9 T on bridges prepared by laser cutting.
For small deposition rates, Ba2Y(Nb/Ta)O6 grows as well oriented, densely distributed nano-columns (d ~ 10 nm). We achieved a pinning force density of 25 GN/m³ at 77 K at the matching field of 2.3 T, which is among the highest values reported for YBa2Cu3O7-x. The field dependence of the pinning force density and the anisotropy of the critical current density show a complex behavior which is explained by a matching effect of the magnetic field’s c-axis component and the superposition of up to three pinning components. The exponent N of the current-voltage characteristics (inversely proportional to the creep rate S) elucidates the depinning mechanism, changing from double-kink excitation below the matching field to pinning-potential-determined creep above.
The authors acknowledge financial support from EUROTAPES, a collaborative project funded by the European Unions's Seven Framework Programme (FP7 / 2007-2013) under Grant Agreement no. 280432.
Author
Dr
Jens Haenisch
(Karlsruhe Institute for Technology)
Co-authors
Mr
Alexander Meledin
(University of Antwerp)
Prof.
Bernhard Holzapfel
(KIT Karlsruhe)
Prof.
Gustaav Van Tendeloo
(University of Antwerp)
Prof.
Judith MacManus-Driscoll
(University of Cambridge)
Mr
Lars Opherden
(IFW Dresden)
Prof.
Ludwig Schultz
(IFW Dresden)
Mr
Marco Bianchetti
(University of Cambridge)
Mr
Max Sieger
(IFW Dresden)
Mr
Patrick Pahlke
(IFW Dresden)
Dr
Rainer Nast
(KIT Karlsruhe)
Dr
Ruben Hühne
(IFW Dresden)
