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چکیده
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In high-temperature ceramic superconductors, vortices motion is induced by the strong thermal fluctuations because of the thermally activated flux flow (TAFF). The TAFF impedes the transport properties and critical current density of superconductors. It has been reported that adding nano-scale impurities can induce artificial pining centers that may improve inter-granular connections and flux pinning strength in ceramic superconductors. Here, the effects of different amounts (0.0–1.0 wt%) of ZnO nanoparticles on the TAFF behavior and zero temperature activation energy of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase have been studied using the modified TAFF model. Moreover, the impacts of the additive on the intergranular traits and the Josephson coupling energy of the superconducting phase have been investigated using AC susceptibility measurements. Vortex phases analysis indicates that all composites show a vortex glass to vortex liquid phase transition at Tg. The vortex liquid phase is divided into the critical region existing in a finite temperature region just above Tg and the TAFF region present in the finite temperature region above it. It was found that the TAFF region is shifted to the higher temperatures and gets narrower, as the ZnO nanoparticles concentration enhances from 0.0 to 0.2 wt%. The vortex glass to vortex liquid transition temperature, Tg, increases from 93.8 K for the sample without additive to 101.0 K for the com posite with 0.2 wt% ZnO nanoparticles. In addition, the zero-temperature activation energy (U0/KB) increases from ~0.4 × 105 K for the sample without additive to ~1.4 × 105 K for the composite with 0.2 wt% ZnO nanoparticles and then decreases for more ZnO concentrations. Moreover, it was found that the Josephson coupling energy Ej increases from ~0.039 eV for the sample without additive to ̴0.136 eV for the composite with 0.2 wt% ZnO nanoparticles. These results point out a significant enhancement of the activation energy, flux pinning capability, and inter-granular coupling of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase with the addition of the 0.2 wt% ZnO nanoparticles.
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