Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 1: Superconductivity - Fabrication, Technical Optimization and Characterization

TT 1.9: Vortrag

Freitag, 4. März 2005, 12:15–12:30, TU H104

J_c enhancement in YBa₂Cu₃O_7−x thin films by metal doping — •J. Hänisch, C. Cai, R. Hühne, B. Holzapfel und L. Schultz — IFW Dresden, Helmholtzstraße 20, 01069 Dresden

Due to the sharp cube textures in RABiTS (rolling assisted biaxially textured substrates) tapes, grain boundaries are not the only J_c limiting factor anymore and flux pinning is now again a focus for further improvement of coated conductors in higher magnetic fields.
In this work, we present a comparative study of the influence of different metallic dopants (D: Ir, Ti, Zr and Hf) on J_c(B). Quasi-multilayer films of 40x(6.5 uc YBCO/n uc D) were prepared by pulsed laser deposition with a stoichiometric YBCO target and a metal target for the dopant, n being in the range of 0.04...0.3. In the case of Ir, nano-particles of BaIrO₃ are growing epitaxially inside the YBCO film. Due to their larger lattice parameter of 4.1 Å compared to 3.9 Å (b-axis) in YBCO, the YBCO structure is under lateral stress. A certain degree of disorder on the Ba sites is expected because of the non-stoichiometry after precipitation. Both introduce extended and random defects respectively and lead to an enhancement in pinning force density and irreversibility field.
In addition, Zn doping is investigated as a possibility to enhance J_c in thin films. At doping levels of x < 0.05%, an increase in J_c in higher magnetic fields was found.