Flux-Pinning of Bi2Sr2CaCu2O8 High Tc Superconducting Tapes Utilizing (Sr,Ca)14Cu24O41 and Sr2CaAl2O6 Defects

Published

February 19, 2017

Author(s)

T J. Haugan, Winnie Wong-Ng, Lawrence P. Cook, L Swartzendruber, H J. Brown, D T. Shaw

Abstract

Efforts to improve the magnetic flux-pinning properties of Bi₂Sr₂Ca₁Cu₂0_{8 +δ /Ag (2212/Ag) tape conductors utilizing (Sr}d1-x^Ca_x)14Cu₂₄0_{41+δ (014x24) and Sr}d2^CaA1₂0₆ (03A1₂) defects are described. Precursor powders with composition (2212 + N vol% Sr₁₀Ca₄Cu₂₄0_41+δ ; N = 0,7,15) were prepared by the solid-state method to obtain X-ray diffraction (XRD) subsolidus phase equilibrium at 860 C. Nanophase (10 nm to 20 nm) Al₂0₃ was added (1.1 wt%) to N = 0 and 15 fully reacted powders. Brush-on coated tapes (13 m to 17 m 2212 thickness) were processed by a partial-melt growth method in air with variable melting from 865 C to 890 C, and slow-cool recrystallization from 856 C to 847 C. The effect of different melt temperatures and compositions on film properties (phase assemblages, orientations, and compositions, and defect sizes) was studied by XRD, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Higher N increased the amount of (Sr_1-xCa_x)Cu0_{2 +δ} (01 x 1) and 014 x 24 defects observed in processed films. Addition of 1.1 wt% A1₂0^3^ for N = 0, 15 powders and melt temperatures (870 C to 900 C) tested had two main effects: (1) A1₂0₃ reacted within less than or equal to} 0 min to 4 min after melting to produce defects with primary composition Sr₂CaA1₂0_{6 + δ} , as verified by XRD and EDS, and (2) dramatically shifted the phase assemblages toward increasing 014x24 and decreasing 01 x 1 defects. The 03A1₂ defects increased to 1 m to 5 m size by coarsening with increasing melting temperatures (approximately equal to} 880 C to 895 C). Magnetic critical current density (J_c) of (N = 15 + alum powder) tapes showed improvement for 1T applied fields in the 20 K to 30 K range. Transport J_c (4.2 K, 0 T) of N = 15 and N = 15+alum composition tapes were approximately equal to} 30 % and approximately equal to} 5 %, respectively, of N = 0 tapes.

Citation

ACerS

Pub Type

Journals

Keywords

(Xr, Ca)₁₄Cu₂₄O_41+γ, Bi₂Sr₂CaCu₂O_8=γ, critical current density, flux pinning, magnetic field, nanophase, partial melt growth, Sr₂CaA 1₂O₆, superconducting tapes

Citation

Haugan, T. , Wong-Ng, W. , Cook, L. , Swartzendruber, L. , Brown, H. and Shaw, D. (2017), Flux-Pinning of Bi₂Sr₂CaCu₂O₈ High T_c Superconducting Tapes Utilizing (Sr,Ca)₁₄Cu₂₄O₄₁ and Sr₂CaAl₂O₆ Defects, ACerS (Accessed April 17, 2024)