Effect of metallic Ag on the properties of Bi-2212 ceramic superconductors
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Effect of metallic Ag on the properties of Bi-2212 ceramic superconductors ¨ zkurt • M. A. Madre • A. Sotelo Berdan O J. C. Diez
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Received: 22 March 2013 / Accepted: 17 April 2013 Ó Springer Science+Business Media New York 2013
Abstract Samples of Bi2Sr2CaCu2AgxOy with small Ag additions (x = 0.05, 0.1 and 0.2) have been prepared by the classical solid state reaction method. The effect of Ag has been investigated using electrical resistivity, scanning electron microscopy, XRD, mechanical and dc-magnetization techniques. It has been found that very small amounts of Ag are enough to improve the physical and magnetic properties of the samples. The best Jc values obtained from dc magnetization measurement (M-H), employing the well known Bean’s critical model, have been obtained for the Bi2Sr2CaCu2Oy samples with 0.05 Ag addition, reaching about 3000 A/cm2 at 15 K, which is a very high value for bulk materials with randomly oriented grains.
1 Introduction As it is well known, the optimization of mechanical and electrical properties of high-temperature superconductors are very important for their application in practical devices. Since the discovery of BSCCO high-temperature superconductors by Maeda et al. [1], it has been found that this family is composed of three different phases, Bi2Sr2CuOx (Bi-2201), Bi2Sr2CaCu2Ox (Bi-2212), and Bi2Sr2Ca2Cu3Ox (Bi-2223). Between them, the Bi-2212 phase has been shown as the most promising due to the easy and quick ¨ zkurt (&) B. O Department of Energy Systems Engineering, Faculty of Tarsus Technology, University of Mersin, Mersin, Turkey e-mail: [email protected] M. A. Madre A. Sotelo J. C. Diez ICMA (CSIC-Universidad de Zaragoza), Marı´a de Luna, 3, 50018 Saragossa, Spain
preparation, together with its relatively high Tc. When considering the practical applications of these superconductors, two main characteristics should be fulfilled: high critical magnetic field (Hc) and high critical current density (Jc). As a consequence, many works have been performed in order to improve Jc and Hc in these materials. Some of them have been based on the doping processes by different elements such as Nb, B, Cd, Sn, Ag, Pb [2–14] or on the synthesis procedures [15–17]. On the other hand, ceramic superconductors possess some intrinsic drawbacks, such as the intergrain weak links and weak flux pinning capability [18]. Some attempts to improve the grains connectivity are based on texturing processes, which have demonstrated an important raise on the transport properties in superconductors [19–21], as well as in other similar systems [22, 23]. Moreover, this raise has been much higher when the texturing processes have been combined with small Ag additions in all cases [3, 7, 24–27]. In these works, it has been found that Ag improves the superconducting and mechanical behaviour of these materials. Unfortunately, the mechanism of the improvement is still not clear, as some works were claiming that Ag acts improving the the grain links while others pointed out it is due to the Ag inco
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