Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 12: Symposium “Coated HTS Conductors”

TT 12.1: Invited Talk

Tuesday, March 27, 2007, 09:30–10:00, H20

Improvement of the Critical Current Density in YBCO Coated Conductors — •Bernhard Holzapfel — IFW Dresden, Helmholtzstr. 20, 01069 Dresden

The Jc limitation mechanism in coated conductors based on biaxially textured metal substrates depends strongly on the applied magnetic field. Up to a texture dependent crossover field, the network of small angle grain boundaries limits Jc. Below this crossover field Jc can be improved by optimizing the grain boundary network. At higher magnetic fields above the crossover field, Jc is limited by the intragrain pinning properties. Here we report on different material aspects connected to the Coated Conductor to improve the overall critical current density. Based on optimized cube textures in recrystallized metal tapes and appropriate buffer layer architectures, Jc of coated conductors at lower magnetic fields can be improved by geometrically tailoring the grain boundary network using cube textured substrates with high aspect ratio grains. For higher magnetic fields, where the intragrain pinning properties limit Jc, our experiments to introduce artificial pinning centres by preparation of quasi-multilayers where sub unit cell thin metal layers were incorporated in Y123 films will be discussed. Due to the oxidizing deposition atmosphere and solid state reaction with the Y123 phase nanometre sized perovskite precipitates, which are epitaxially incorporated into the Y123 lattice, are formed. Pinning properties and Jc anisotropy at various fields and temperatures were analyzed. At 77K irreversibility fields up to 10.3T were observed in Y123 quasi-multilayers containing nano-sized BaHfO3 precipitates.