Flux-Pinning of Bi2Sr2CaCu2O(8 + delta) High Tc Superconducting Tapes Utilizing (Sr,Ca)14Cu24O(41 + delta) and Sr2CaAl2O6 Defects

Abstract : Efforts to improve the magnetic flux-pinning properties of Bi2Sr2CaCu2O(8+delta)/Ag (2212/Ag) tape conductors utilizing (Sr(1-x)Ca(x)14Cu24O(41+delta) and Sr2CaAl2O6 defects are described. Precursor powders with composition(2212 + N% volume fraction Sr10Ca4Cu24O(41+delta); N = 0, 7, 15) were prepared by solid-state reaction to obtain subsolidus phase equilibrium at 860 deg C, as measured by X-ray diffraction (XRD). Nanophase (10 - 20 nm)Al2O3 was added (1.1% mass fraction) to N = 0 and 15 fully reacted powders. Brush-on coated tapes (13 - 17 micrometers 2212 thickness) were processed by a partial-melt growth method in air with variable melting from 865 deg C to 890 deg C, and slow-cool recrystallization from 856 deg C to 847 deg 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).