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    Bulk ngB2 superconductor production by excess Mg and hot press methods and their properties
    (2017) Yanmaz, Ekrem; Cingi, Didem Odabaşı; Alcan, Pelin; Saraçoğlu, İlkay; Berrio, Claudia Castillo; Alkan, Ümit; Ülgen, Asaf Tolga
    Four different nominal compositions MgB, MgB, MgB and MgB were produced by excess Mg method and hot press. These superconducting samples were compared in terms of structural, electric and magnetic properties. The superconducting phase was determined by XRD analysis, which indicated the formation of MgB structure as a main matrix with some amount of nonsuperconducting phases, such as metallic Mg and minor amount of MgO. The electric properties of the samples were characterized by low temperature resistivity measurements under different magnetic fields 0.5, 1.0, 3.0 T. The results showed that the superconducting Tc,onset and Tc,offset transition temperatures moved to lower values. These results indicate that excess Mg method improves the superconducting and magnetic properties of MgB, as well as enhanced the rigidity and ductility of the samples. Experimental results showed the advantages of the proposed methods, established the most suitable transition temperature of the samples, as well as the decline from the superconducting to normal state
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    Structural and physical properties of sm-doped Bi1.6Pb0.4Sr2Ca2-xSmxCu3Oy superconductors
    (Elsevier Science Bv, 2005) Terzioğlu, Cabir; Yılmazlar, Mustafa; Öztürk, Özgür; Yanmaz, Ekrem
    The superconducting Bi1.6Pb0.4Sr2Ca2-xSMxCu3Oy (X = 0.0, 0.0005, 0.001, 0.005, 0.01, 0.1, 0.5, 1.0, and 1.5) system was investigated for different concentrations of Sm. The structural analysis was carried out by XRD. XRD results show that the samples with substitution of various amounts of Sm for Ca transform from the major high-T-c phase (Bi-2223) to the low-T-c phase (Bi-2212). The lattice parameter data extracted from XRD showed that with increasing Sm concentration (x), the lattice parameter a increases slightly while the lattice parameter c decreases significantly. DC resistivity measurements were carried out by the standard four-probe technique in the temperature range between 25 K and 130 K. With increasing Sm substitution up to x = 0.1, the values of T-e(offset) vary between 107 K and 70 K. The samples with x > 0.1 did not show any superconducting transition down to 25 K. The critical current density measurements were performed in liquid nitrogen. Critical current density decreases with increasing Sm substitution, and it was measured to be 43 A/cm(2) for the sample with x = 0.0 at zero field. Microstructure examinations were carried out by SEM. All the reported data were discussed, and compared with earlier results on Sm and other substituted Bi-Sr-Ca-Cu-O system.