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

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Author(s): T J. Haugan; Winnie K. Wong-Ng; Lawrence P. Cook; L Swartzendruber; H J. Brown; D T. Shaw;
Title: Flux-Pinning of Bi2Sr2CaCu2O8 High Tc Superconducting Tapes Utilizing (Sr,Ca)14Cu24O41 and Sr2CaAl2O6 Defects
Published: Date Unknown
Abstract: Efforts to improve the magnetic flux-pinning properties of Bi2Sr2Ca1Cu208 +δ /Ag (2212/Ag) tape conductors utilizing (Srd1-x^Cax)14Cu24041+δ (014x24) and Srd2^CaA1206 (03A12) defects are described. Precursor powders with composition (2212 + N vol% Sr10Ca4Cu24041+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 (Sr1-xCax)Cu02 +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 Sr2CaA1206 + 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 (Jc) of (N = 15 + alum powder) tapes showed improvement for 1T applied fields in the 20 K to 30 K range. Transport Jc (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
Keywords: (Xr,Ca)14Cu24O41+γ;Bi2Sr2CaCu2O8=γ;critical current density;flux pinning;magnetic field;nanophase;partial melt growth;Sr2CaA 12O6;superconducting tapes
Research Areas: Characterization, Ceramics