Structural, Magneto-Resistivity and Magnetization Investigations of Y(Ba1-xMgx)2Cu3O7-δ Superconducting System
Ö. Çiçek, K. Yakinci
Department of Basic Engineering Sciences, Faculty of Engineering and Natural Sciences, İskenderun Technical University, 31200, İskenderun/Hatay, Turkey
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In this study, YBCO superconducting samples with the nominal composition of Y(Ba1-xMgx)2Cu3O7-δ, where x=0.0, 0.5, 1.0, and 1.5, were prepared by the solid-state method to get better superconducting properties. Structural, electrical transport, and magnetic characterizations up to ±9 T applied fields were performed, including calculations of the upper critical field Hc2(0), irreversibility field μ0Hirr, activation energy U0(J,T,H), and pinning force Fp, and the obtained results were presented the first time for the Mg substitution to a Ba site in an optimally-doped YBCO superconducting system. It was found that the crystal parameters changed with the Mg substitution, but the crystal symmetry remained unchanged. Two impurity phases, Y-211 and MgO, were grown and became dominant at high substitution ratios. The superconducting properties of the samples deteriorated with the substitution of Mg; even high MgO substituted samples showed no superconducting properties. Deteriorations were also obtained in the properties Hc2(0), μ0Hirr, U0(J,T,H), and Fp. Two important points are thought to be responsible for these deteriorations. (i) MgO is not being able to be fully resolved in the matrix. Therefore, instead of Mg replacing with Ba, MgO remains in the impurity phase. As a result of this, the Ba concentration in the structure gradually decreases, and then the superconductivity is destroyed. (ii) The samples shift from the optimally doped region to the over-doped region due to the increase in hole concentration.

DOI:10.12693/APhysPolA.142.478
topics: YBCO superconductors, activation energy, upper critical field, irreversibility field