Activation energy U(H) and pinning behavior of Yb-impurity-diffused YBa 2Cu 3O 7-x
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Superconducting Y123 samples were prepared by the solid-state reaction (SSR) method. To get a layer of Yb (thickness ?4 ?m) on the surface of one side of the sample an ultrahigh-vacuum electron-beam deposition system was used and Yb diffusion in Y123 was carried out thermally. The energy dispersive X-ray fluorescence technique (EDXRF) was used for the determination of the concentration of Yb atoms in the diffusion regions of Y123 samples. It was found that when the diffusing-annealing temperature increased the transition became much sharper and the sharpest transition was observed for the sample diffused at 900°C The activation energy of all samples was estimated from the resistivity curves using the TAFF model. It has been revealed that the pinning properties and activation energy improve when the diffusionannealing temperature increases for a convenient temperature and also the activation energies of Ybdiffused samples are larger than that of an undoped Y123 sample. © 2007 WELEY-VCH Verlag GmbH & Co. KGaA.