Facile and Cost-Effective Synthesis and Deposition of a YBCO Superconductor on Copper Substrates by High-Energy Ball Mil
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INTRODUCTION
HIGH-TEMPERATURE superconductors (HTCs), or type 2 superconductors, are those comprised of metallic compounds or alloys that display critical temperatures as high as 144 K ( 129 C), especially for materials that cannot be formed stoichiometrically.[1] These materials exhibit flux pinning and levitation abilities when placed in a magnetic field and, hence, have manifold potential for useful industrial and energy storage applications.[2,3] Different materials have been studied for the superconducting effect at high temperature ever since the Ba-La-Cu-O compound developed by Bendorz and Mu¨ller, which displayed a critical temperature of 36 K (237 C).[4] This discovery led to further investigations on compounds with similar cuprate structures that contain blocks of conducting CuO2 planes,[5] which eventually resulted in the discovery of Y1Ba2Cu3O7 (123 or YBCO) with a critical temperature of 93 K ( 180 C), a temperature reached with a nonstoichiometric balance of Y1Ba2Cu3O6.95.[1] YBCO, a ceramic superconductor that exhibits d-wave electron pairing, has been the most studied material due to its unique structure and configuration and was preferred, as its critical temperature is above that of the boiling point of liquid nitrogen.[6]
ABDUL HAI ALAMI, Associate Professor, is with the Sustainable and Renewable Energy Engineering Department, University of Sharjah, P.O.Box 27272, Sharjah W9124, United Arab Emirates, and also with Center for Advanced Materials Research (CAMR), University of Sharjah. Contact email: [email protected] MHD ADEL ASSAD and CAMILIA AOKAL, Research Assistants, are with the Sustainable and Renewable Energy Engineering Department, University of Sharjah. Manuscript submitted April 7, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
Synthesis of YBCO throughout the literature can be categorized into three main techniques: solid-state synthesis, solution techniques, and vapor/plasma processes.[7] Two of the most recent synthesis techniques include the synthesis of YBCO powder by the oxalic acid precipitation method and the synthesis of YBCO nanowires with anodic aluminum template.[8,9] Of the three, the conventional ceramic process categorized under the standard solid-state synthesis technique of oxide powders is by far the most widely used method for YBCO synthesis where powders of yttrium oxide, barium carbonate and cupric oxide are ground according to the required compositions (1:2:3 ratio of Y:Ba:Cu) and then later calcinated with intermediary grinding. Annealing the mixture at a temperature of 500 deg was also required to achieve the required oxygen content. However, this method results in weak link grain boundaries and anisotropic superconductivity, leading to a low critical current density also promoted by randomness of grain distribution.[8] Applications of YBCO powders include the production of thin films, YBCO tapes, and YBCO-coated conductors.[9–11] For recent applications that endure overcoming the expense of energy storage practices, superconducting coils such as YBCO are used in
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