CUED Publications database

A new seeding technique for the reliable fabrication of large, SmBCO single grains containing silver using top seeded melt growth

Shi, YH and Dennis, AR and Cardwell, DA (2015) A new seeding technique for the reliable fabrication of large, SmBCO single grains containing silver using top seeded melt growth. Superconductor Science and Technology, 28. ISSN 0953-2048

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© 2015 IOP Publishing Ltd. Silver (Ag) is an established additive for improving the mechanical properties of single grain, (RE)Ba 2 Cu 3 O 7 -δ [(RE)BCO, RE=Sm, Gd and Y] bulk superconductors. The presence of Ag in the (RE)BCO bulk composi tion, however, typically reduces the melting temperature of the single crystal seed in the top seeded melt growth (TSMG) process, which complicates significantly the controlled nucleation and subsequent epitaxial growth of a single grain, which is essential for high field engineering applications. The reduced reliability of the seeding process in the presence of Ag is particularly acute for the SmBCO system, since the melting temperature of SmBCO is very close to that of the generic NdBCO(MgO) seed. SmBCO has a high superconducting transition temperature, T c , and exhibits the most pronounced 'peak' effect at higher magnetic field of all materials in the family of (RE)BCO bulk superconductors and, therefore, has the greatest potential for use in practical applications (compared to GdBCO and YBCO, in particular). Development of an effective seeding process, therefore, is one of the major challenges of the TSMG process for the growth of large, high quantity single grain superconductors. In this paper, we report a novel technique that involves introducing a buffer layer between the seed crystal and the precursor pellet, primarily to inhibit the diffusion of Ag from the green body to the seed during melt processing in order to prevent the melting of the seed. The success rate of the seeding process using this technique is 100% for relatively small batches of samples. The superconducting properties, critical temperature, T c , critical current density, J c and trapped fields, of the single grains fabricated using the buffers are reported and the microstructures in the vicinity of the buffer of single grains fabricated by the modified technique are analysed to understand further the effects of buffers on the growth process of these technologically important materials.

Item Type: Article
Divisions: Div C > Materials Engineering
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:40
Last Modified: 22 Sep 2017 20:12