Effect of Fe Substitution for Cu on Microstructure and Magnetic Properties of Laser Floating Zone (LFZ) Grown Bi-2212 Ro
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O R I G I N A L PA P E R
Effect of Fe Substitution for Cu on Microstructure and Magnetic Properties of Laser Floating Zone (LFZ) Grown Bi-2212 Rods M. Ozabaci · A. Sotelo · M.A. Madre · M.E. Yakinci
Received: 8 November 2012 / Accepted: 30 November 2012 / Published online: 29 December 2012 © Springer Science+Business Media New York 2012
Abstract In this paper, the laser floating zone (LFZ) technique has been used to fabricate Bi2 Sr2 Ca1 Cu2−x Fex O (x = 0, 0.01, 0.03, 0.05, 0.1) superconducting fibers. The effects of Fe substitution on grain alignment and superconducting properties of annealed fibers were studied using SEM/EDX microanalysis in addition to phase analysis and magnetic measurements realized through XRD, M–T , and M–H loops. In the same growth conditions, higher Fe contents lead to a more compact microstructure with lower porosity but also caused the formation of poor superconducting phases followed by the decrease of Tc and Jcmag . No evidence of enhanced pinning capability was found in the magnetic measurements. Annealed rods indicated a weakly ferromagnetic-like behavior at relatively high doping levels. Keywords Bi-2212 · Fe substitution · LFZ · Texture · Melt processing
1 Introduction Just after the discovery of superconductivity in copper-based oxides, great efforts have been made in order to find the M. Ozabaci () · M.E. Yakinci SEM/EDX Laboratuvarı, Bilimsel ve Teknolojik Ara¸stırma Merkezi (˙IBTAM), ˙Inönü Üniversitesi, 44280, Malatya, Turkey e-mail: [email protected] A. Sotelo · M.A. Madre Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Maria de Luna, 3, 50018, Zaragoza, Spain M.E. Yakinci Fizik Bölümü, Fen Edebiyat Fakültesi, ˙Inönü Üniversitesi, 44280, Malatya, Turkey
basic parameters which are responsible for the superconducting properties of these compounds [1, 2]. Among highTc superconducting (HTS) systems, Bi-based cuprates deserved special attention owing to their promising chemical stability, absence of rare earths, relatively high critical temperature and, when properly processed, high critical current density. From the point of view of technological applications, preparation techniques of superconducting materials are so important as the material type. When the current-carrying capacity of the material is regarded, it is seen that the major limitations come from intergrain weak links and weak flux pinning capabilities for the superconducting materials. Oriented grains together with artificially doped structures have been considered to be effective solutions to overcome these limitations. Within this scope many different techniques have been developed so far to obtain materials with highly aligned grains [3–6]. Of all these techniques, the Laser Floating Zone (LFZ) technique has been shown to be an outstanding technique in terms of grain alignment, reproducibility, speed, and cost. This technique has been successfully applied so far for the high-Tc superconductors, especially for the Bi-2212 phase, as well as on similarly layered materials
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