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    Effect Y substitution on the microstructure, transport and magnetic proprieties of Bi2Sr2Ca1Cu2O8+? superconducting ceramics
    (Walter de Gruyter GmbH, 2016) Menassel, S.; Mosbah, M.-F.; Boudjadja, Y.; Altintas, S.P.; Varilci, A.; Terzioglu, C.
    In high Tc superconductors (HTSC) the activation energy gives information about the pinning properties of a sample under applied magnetic field. Pinning of vortices determines the critical current density Jc which is of great importance for practical applications of HTSC. Instead of magnetic measurements, the activation energy may be calculated from resistivity measurements realized under magnetic field. This kind of measurement has been made in this work for yttrium doped samples of Bi2Sr2CaCu2O8+d (Bi-2212) for different values of applied magnetic field. Samples of Bi2Sr2Ca1-xYxCu2O8+d (x = 0, 0.025, 0.1, 0.25) were prepared by a sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of X-ray. The measurements of resistivity were made using a classical four probe method and DC current. The magnetic field was applied with a constant amplitude of 0 T, 1 T, 2 T and 3 T. The obtained results show that the activation energy decreases with introduction of yttrium, but has a relative maximum when x is equal 0.1. The decrease of the activation energy is explained by the granular nature of the samples which promotes 3D transition to 2D of the vortex lattice. © 2016 Wroclaw University of Technology.
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    Support of polaronic states and charge carrier concentrations of YBa2Cu3O7-y ceramics by oxygen and Mn2O3 impurity
    (Wiley, 2024) Kurtul, Gulnur; Yildirim, Gurcan; Turgay, Tahsin; Terzioglu, C.
    The influence of oxygen and Mn2O3 impurity addition intervals 0.01 <= x <= 0.30 on the basic electrical conductivity, stabilization, crystallinity quality, grain boundary couplings, structural, orbital hybridization mechanisms, and superconducting properties of YBa2Cu3O7-yMnx ceramics has extensively been analyzed by electrical resistivity, X-ray diffraction investigations, and related theoretical results. It has been found that there is a strong link between the production conditions and fundamental characteristic features. All the results deduced have enabled us to discuss the variation of electron-electron and electron-phonon interactions, order parameter for super-electrons and cooper-pairs, organization of Cu-O coordination, homogeneities of oxidation states, microscopic structural problems, electronic density states, and grain boundary couplings between the adjacent layers in the YBa2Cu3O7-y ceramics. Similarly, we have discussed the change in the formation of pairing mechanisms and bipolarons in the polarizable lattices in the microdomain clusters. The results have shown that both the presence of oxygen and optimum manganese impurity of x = 0.07 led to the enhancement in the fundamental characteristic features related to the basic physical, quantum mechanical, and thermodynamics features. Thus, the material produced at the most ideal conditions has exhibited the best orthorhombic crystal structure with the distortion degree of 6.419 x 10(-3), paring mechanism, and crystallinity quality due to the development of orthorhombicity and oxygen ordering degree. Namely, the addition of optimum manganese impurity has organized the Cu-O coordination and stabilized the crystal structure as much as possible. Numerically, the sample prepared with x = 0.07 Mn ions has displayed the largest crystallite size, c-axis length, residual resistivity ratio, onset, and offset critical temperatures of 10.977, 11.723 & Aring;, 73 nm, 98.320 K, and 100.504 K, respectively. Conversely, the same material has demonstrated the smallest oxygen ordering degree of 6.714, strain of 44.015 x 10(-3), and a- and b-axis lengths of 3.792 and 3.841 & Aring;. On the other hand, the oxygen-free annealing condition and excess manganese impurity have completely damaged the whole mechanism because of the phase transition from orthorhombic to tetragonal (structural O-T transition) crystal structure. To sum up, the oxygen and optimum manganese impurity have encouraged the YBa2Cu3O7-y superconductors to use in much more application fields.