J c enhancement and flux pinning of Se substituted YBCO compound
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Jc enhancement and flux pinning of Se substituted YBCO compound Z. D. Yakinci • D. M. Gokhfeld • E. Altin • F. Kurt • S. Altin • S. Demirel • M. A. Aksan M. E. Yakinci
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Received: 19 June 2013 / Accepted: 27 August 2013 / Published online: 13 September 2013 Ó Springer Science+Business Media New York 2013
Abstract Y2/3 Se1/3Ba2Cu3Ox compound was fabricated by using solid state fabrication technique. Optimum heat treatments conditions for Y0.77Se0.33Ba2Cu3Ox were investigated. It was determined that the XRD results of these samples were similar to Y-123 phase with some impurities. Magnetization dependence of applied magnetic fields was measured in the range of 0–9 T at 10–50 K. The symmetric and asymmetric M–H loops were obtained for the samples. Magnetization loops obtained from measurements were successfully described by the extended Valkov–Khrustalev model. The temperature and applied magnetic field dependencies of magnetization of sample were estimated and critical current density of samples was calculated by Bean model and pinning force of samples was calculated by using Lorentz force. It is found from critical current density values that Se additions were acted as a pinning center which increased critical current density.
Z. D. Yakinci Saglik Hizmetleri Meslek Yuksek Okulu, Inonu Universitesi, 44280 Malatya, Turkey D. M. Gokhfeld L.V. Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk, Russia E. Altin F. Kurt S. Demirel (&) Bilimsel ve Teknolojik Arastrma Merkezi, Inonu Universitesi, 44280 Malatya, Turkey e-mail: [email protected] S. Altin M. A. Aksan M. E. Yakinci I˙nonu Universitesi, Fen Edebiyat fakultesi, Superiletkenlik Arastirma Grubu, Inonu Universitesi, 44280 Malatya, Turkey
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1 Introduction After discovery of superconductivity in the YBa2Cu3O7-d (YBCO) system above liquid nitrogen temperature (77 K) [1], scientists have spent much effort to increase the superconducting transition temperature, Tc, and critical current, Jc. For this purpose, different preparation techniques, dopings/substitutions and additions to the system were performed. Three different phases are presented in the YBCO system: Y-123, Y-124 and Y-247 with the Tc values at 90, 80 and 80 K, respectively [2–5]. Y-123 system has a special importance due to high current carrying capacity at 77 K and high critical magnetic field, Hc [6, 7]. Jc of the system strongly depends on the Cu-chains which control the carrier density at the CuO planes [8] and so the Tc value [9, 10]. It is expected that the increasing CuO planes in unit cell can cause an increase in the Tc value of the system. However, the highest Tc value was obtained only in Y-123. The superconducting properties depend strongly on stoichiometry of the HTc YBCO system. Small changes in the stoichiometry, especially deficiency of Ba and Cu, can significantly influence the properties of YBCO. Yoshikate et al. investigated the Cu deficiency in the YBCO system. They found that the crystal structure changed significantly even with small change in the copper conten
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