Comparison of the superconducting properties of Y-Ba-Cu-O and Y-Ba-Cu-O-Ag bulk superconductors

J V J Congreve,D A Cardwell,A R Dennis,J H Durrell,Y H Shi

doi:10.1088/1757-899x/502/1/012181

J V J Congreve, D A Cardwell + Show 3 more

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https://doi.org/10.1088/1757-899x/502/1/012181

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Abstract

The widespread use of RE-Ba-Cu-O [(RE)BCO] bulk superconductors, where RE=Y, Gd or Sm, in practical applications requires large single grains that exhibit uniform superconducting properties. Until recently, however, it was difficult to grow successfully YBCO-Ag bulk materials in the required single grain form, due primarily to the relative complexity of the top seeded melt growth process (TSMG) and the introduction of an alloying element (Ag) to the precursor composition. In most cases, alloying elements are used to improve the mechanical properties of the bulk superconductor whilst, at the same time, aim to cause minimal detrimental effect on the superconducting properties of the fully processed sample. In this work we investigate the effect of the addition of silver to YBCO on the superconducting properties of the bulk single grain, including trapped field, Tc and Jc, and on the sample microstructure.

Highlights

IntroductionFollowing significant research over the past thirty years on the fabrication of (RE)BCO in the form of large single grains [16, 17], the so-called top seeded melt growth technique (TSMG) is used routinely to fabricate large single grains of a wide range of (RE)BCO bulk superconductor compositions [14, 18]
Single grain range of (RE)-Ba-Cu-O [(RE)BCO] bulk high temperature superconductors, where RE = Y, Gd or Sm, are able to trap significantly larger magnetic fields than those generated by permanent magnets [1, 2]
We report the use of liquid-phase enriched top seeded melt growth process (TSMG) technique [21] to grow reliably large single grains of YBCO-alloying element (Ag) bulk superconductor [22]

Summary

Introduction

Following significant research over the past thirty years on the fabrication of (RE)BCO in the form of large single grains [16, 17], the so-called top seeded melt growth technique (TSMG) is used routinely to fabricate large single grains of a wide range of (RE)BCO bulk superconductor compositions [14, 18]. This process involves heating the compacted precursor powder to the peritectic decomposition temperature to enable the superconducting YBa2Cu3O7-δ (Y-123) phase to decompose into a secondary, non-superconducting Y2BaCuO5 (Y-211) solid phase and a residual Ba-Cu-O liquid phase. Slow, controlled undercooling in the presence of a suitable solid seed crystal enables the nucleation and growth of a large single grain consisting of a continuous, superconducting Y-123 phase matrix containing a distribution of discrete, non-superconducting embedded Y-211 phase inclusions [14, 19]

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