Weak Links and Critical Current Anisotropy in Melt-Textured HTSC Ceramics Studied by Magneto-Optical Express Control
YBa2Cu3O7-x ceramics were prepared by the modified melt textured process on the poly-crystalline substrate of the Y2BaCuO5 composition. Magneto-optical technique with the ferrogarnet films as sensor was used for visualization of magnetic flux distribution and their evalution under remagnetization of specimens. The pictures of weak links visualized by the magneto-optical technique were correlated with the sample macro- and microstructure, studied by X-ray topography, electron (SEM) and polarization light microscopy. The role of different details of the structural peculiarities of the specimens in the weak links formation was analyzed and the problem of critical current anisotropy was reviewed. The weak links behavior under the magnetic field variation was studied in the details. The pinning centers, weak links, its dependence upon the (2.11) concentration, the particle size as well as its role in Jc value formation were discussed. Experimental values of the critical current density varied from 2 104 up to (5+8) 105 A cm-2 for the regions of specimen with the different structures. We report the first real time direct magneto-optic images of the isotropic magnetic flux distribution in the area of the sample which initially was substrate 211. The principal possibility of our modified method for obtaining highly textured isotropic Y-Ba-Cu-O ceramics capable of carrying current density up to 106 A cm-2 was discussed.
KeywordsMagnetic Flux Weak Link Flux Flow Magnetic Flux Leak Single Arrow
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