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ABSTRACT: Series of (YBa2Cu3O7−δ
)1−x
(Al2O3)
x
samples have been prepared using solid state reaction method. Various amount of nano-sized Al2O3 particles (∼50nm) were added with (x=0, 0.005, 0.01, 0.02, and 0.05). The microstructure and the morphology of the polycrystalline samples have been characterized
by X-ray diffraction (XRD) and atomic force microscopy (AFM). The magneto-transport properties of these samples were investigated
using resistance–temperature (R–T) and current–voltage (I–V) characteristics. All samples showed an orthorhombic structure with a tendency to transformation to tetragonal phase at higher
levels of nanoparticles addition. The morphology of the surface of pure samples reveals a considerable number of weak-links,
randomly oriented and clean grain boundaries. While in samples with nano inclusions, grain boundaries were filled with nanosized
particle and have less number of weak-links. Significant enhancement of the superconducting critical current density J
c
in applied magnetic field was observed due to nano Al2O3 inclusions. However, further increase in the value of x decreases the transition temperature T
c
and the critical current density J
c
. These results were interpreted in terms of the flux pinning mechanisms in granular superconducting networks which leads
to a better basic understanding of the performance of YBCO system in high applied magnetic fields.
KeywordsYBCO-Al2O3 nanoparticles-Critical current density-X-ray diffraction-Atomic force microscopy
Journal of Superconductivity and Novel Magnetism 04/2012; 23(7):1333-1340. · 0.65 Impact Factor
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ABSTRACT: MgB2 polycrystalline superconducting specimens were irradiated with 10 MR and 20 MR doses of γ-rays. An increase in the normal state resistance and a broadening of the resistive transition to the superconducting state were observed with increasing γ-irradiation dose within the temperature range of 28 –31 K. The change in the critical temperature, Tc was found to be insignificant after irradiation. The critical current density, Jc was found to be enhanced almost at all temperatures after irradiation. The enhancement of Jc was found to be linear with the irradiation dose at all temperatures. These results are explained by the effects of γ-rays and temperature on the migration of MgO impurities into the grains and the oxygen segregation in the grain boundaries.
Journal of Physics Conference Series 03/2009; 153(1):012010.
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ABSTRACT: Superconducting thick films of Bi1.8Pb0.4Sr2Ca2.2Cu3Ox (BPSCCO) have been prepared on MgO single crystal substrates by employing a screen-printing method. Using this technique, we have prepared several samples utilizing different experimental conditions. Optimization of properties such as film thickness, microstructure, phase formation and annealing time was carefully monitored to obtain samples with transport properties that are quite sensitive to relatively low magnetic fields. The thick film was characterized using XRD, SEM, I–V characteristics and magnetoresistance methods. The microstructural analysis revealed that the samples were superconducting with the existence of a considerable number of weak links between the grains and at the grain boundaries. When the R–B curves were plotted at T = 77 K and at relatively low applied magnetic fields up to 100 G, the value of the normalized resistance was well fitted to the relation R (B)/R (B = 0) = 1 + αB2, where α is a constant. Samples were also measured after several thermal cycles to check the reproducibility at various experimental conditions. It was demonstrated that the I–V curves were independent of the number of thermal cycles and exhibited no significant change at relatively low currents and magnetic fields. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (A) Applications and Materials 06/2008; 205(8):1851 - 1854. · 1.46 Impact Factor
