Processing and Properties of Bar-Shaped Single-Seeded and Multi-Seeded YBCO Bulk Superconductors by a Top-Seeded Melt Growth Technique

Abdulmajeed Almalki,K. Y. Huang,Anthony R. Dennis,J. H. Durrell,Devendra K. Namburi,David A. Cardwell,Mazen Ba-Abbad,Abdul-Aziz Almutairi

doi:10.1007/s10948-016-3944-x

Abstract

The fabrication of (RE)-Ba-Cu-O bulk superconductors, where RE is a rare-earth element such as Y, Gd and Sm, is both time consuming and expensive due to the complexity of the melt process and the slow growth rate of large, single grains. In this study, different approaches to the fabrication of bar-shaped, bulk YBCO superconductors are investigated and compared using single- and multiple-seeding techniques via top-seeded melt growth (TSMG). Both the microstructural and superconducting properties of the bulk samples are investigated, including trapped field, critical current density, critical temperature and levitation force. The results of this study indicate that, in general, the superconducting properties of YBCO fabricated by a single-seeded process are significantly better than those of samples fabricated by a four-seeded process for non-bridge seeds. The differences between the samples are less pronounced in the levitation force measurements, however. In this paper, we attempt to explain the reasons for the similarities and differences observed between bulk samples fabricated by the different single- and multi-seeded processes.

Highlights

Y-Ba-Cu-O (YBCO), and the related cuprates containing different rare-earth (RE) elements, is one of the so-called type II, high-temperature superconducting oxide ceramic materials with a critical temperature of 90–92 K [1, 2]
The trapped magnetic flux density is proportional to the critical current density (Jc) and the diameter of the supercurrent loop (d), i.e. Bt ∝ Jc×d, which is an important figure of merit for bulk superconductors [5]
The NdBCO thin film seeds used to grow YBCO were damaged partly during processing due to contact with the liquid-phase components at elevated temperature [20, 21], which resulted in the undesirable growth of Y-123 grains with a 001/103 orientation

Summary

Introduction

Y-Ba-Cu-O (YBCO), and the related cuprates containing different rare-earth (RE) elements, is one of the so-called type II, high-temperature superconducting oxide ceramic materials with a critical temperature of 90–92 K [1, 2]. The increasing drive towards applications requires the development of methods to produce larger (RE)BCO bulk samples both reliably and economically In this context, multi-seeding is one approach that can be used to fabricate large-sized (RE)BCO in quasi-single grain form and reduce simultaneously the processing time. The NdBCO thin film seeds used to grow YBCO were damaged partly during processing due to contact with the liquid-phase components at elevated temperature [20, 21], which resulted in the undesirable growth of Y-123 grains with a 001/103 orientation This partial melting of seed crystals can be avoided to a certain extent by invoking either two-step cooling during the melt process [22] or by employing the buffer technique [23,24,25]. We compare the key applied properties of single-seeded and multi-seeded YBCO bar-shaped samples in order to determine whether multi-seeding represents an effective route for the production of larger samples, as required in several applications

Experimental Details

Results and Discussion

Conclusion