Control of Y-211 content in bulk YBCO superconductors fabricated by a buffer-aided, top seeded infiltration and growth melt process
Palmer, Kysen G
Dennis, Anthony R
Superconductor Science and Technology
Institute of Physics
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Namburi, D. K., Shi, Y., Palmer, K. G., Dennis, A. R., Durrell, J. H., & Cardwell, D. A. (2016). Control of Y-211 content in bulk YBCO superconductors fabricated by a buffer-aided, top seeded infiltration and growth melt process. Superconductor Science and Technology, 29 (034007)https://doi.org/10.1088/0953-2048/29/3/034007
Bulk (RE)–Ba–Cu–O ((RE)BCO, where RE stands for rare-earth), single grain superconductors can trap magnetic fields of several tesla at low temperatures and therefore can function potentially as high field magnets. Although top seeded melt growth (TSMG) is an established process for fabricating relatively high quality single grains of (RE)BCO for high field applications, this technique suffers from inherent problems such as sample shrinkage, a large intrinsic porosity and the presence of (RE)$_2$BaCuO$_5$ (RE-211)-free regions in the single grain microstructure. Seeded infiltration and growth (SIG), therefore, has emerged as a practical alternative to TSMG that overcomes many of these problems. Until now, however, the superconducting properties of bulk materials processed by SIG have been inferior to those fabricated using the TSMG technique. In this study, we identify that the inferior properties of SIG processed bulk superconductors are related to the presence of a relatively large Y-211 content (~41.8%) in the single grain microstructure. Controlling the RE-211 content in SIG bulk samples is particularly challenging because it is difficult to regulate the entry of the liquid phase into the solid RE-211 preform during the infiltration process. In an attempt to solve this issue, we have investigated the effect of careful control of both the infiltration temperature and the quantity of liquid phase powder present in the sample preforms prior to processing. We conclude that careful control of the infiltration temperature is the most promising of these two process variables. Using this knowledge, we have fabricated successfully a YBCO bulk single grain using the SIG process of diameter 25 mm that exhibits a trapped field of 0.69 T at 77 K, which is the largest value reported to date for a sample fabricated by the SIG technique.
bulk superconductor, (RE)BCO, infiltration and growth, control of RE-211, flux pinning, trapped field, YBCO
This work was supported by King Abdulaziz City for Science and Technology (KACST) and the Engineering and Physical Sciences Research Council (EPSRC, grant number EP/K02910X/1). Additional data related to this publication are available at the University of Cambridge data repository [http://www.repository.cam.ac.uk/handle/1810/252341]. All other data accompanying this publication are available directly within the publication.
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External DOI: https://doi.org/10.1088/0953-2048/29/3/034007
This record's URL: https://www.repository.cam.ac.uk/handle/1810/253209