The addition of mixed double perovskite Ba2Y(Nb/Ta)O6 (BYNTO) to YBa2Cu3O7−δ (YBCO) thin films leads to a large improvement of the in-field current carrying capability. For low deposition rates, BYNTO grows as well-oriented, densely distributed nanocolumns. We achieved a pinning force density of 25 GN/m3 at 77 K at a matching field of 2.3 T, which is among the highest values reported for YBCO. The anisotropy of the critical current density shows a complex behavior whereby additional maxima are developed at field dependent angles. This is caused by a matching effect of the magnetic fields c-axis component. The exponent N of the current-voltage characteristics (inversely proportional to the creep rate S) allows the depinning mechanism to be determined. It changes from a double-kink excitation below the matching field to pinning-potential-determined creep above it.
Self-assembled, segmented nanorods of
c-axis-aligned
Ba2(Y /Gd)(Nb/Ta)O6
as well as randomly distributed nanoparticles of
(Y /Gd)2O3 and
(Y /Gd)Ba2Cu4O8 were grown
into YBa2Cu3O7 − δ
(YBCO) thin films by pulsed-laser deposition. The complex pinning
landscape proves to be extremely effective, particularly at higher fields
where the segmented vortices yield a plateau in critical current density (Jc) with field angle
around 60°. In 0.3
µm thick films, the
Jc values are
higher than 1 MA cm − 2
at 2.5 T ( axis). Owing to the combined interactions of the vortices with the different pinning
centres, interesting new features are observed at high fields in the angular dependence of
Jc.
We report on compositional tuning to create excellent field-performance of Jc in “self-doped,” GdBa2Cu3O7−y (GdBCO) coated conductors grown by ultrafast reactive co-evaporation. In order to give excess liquid and Gd2O3, the overall compositions were all Ba-poor and Cu-rich compared to GdBCO. The precise composition was found to be critical to the current carrying performance. The most copper-rich composition had an optimum self-field Jc of 3.2 MA cm−2. A more Gd-rich composition had the best in-field performance because of the formation of low coherence, splayed Gd2O3 nanoparticles, giving Jc (77 K, 1 T) of over 1 MA cm−2 and Jc (77 K, 5 T) of over 0.1 MA cm−2.
Pulsed laser deposited thin Y Ba2Cu3O7−x (YBCO) films with pinning additions of 5 at. % Ba2Y TaO6 (BYTO) were compared to films with 2.5 at. % Ba2Y TaO6 + 2.5 at. % Ba2Y NbO6 (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films.
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