Transport critical current density of Bi–Sr–Ca–Cu–O/Ag superconductor tapes with addition of magnetic nanopowder γ-Fe2O3

摘要

The effect of sintering temperature on the transport properties of Ag-sheathed-(Bi_1.6Pb_0.4)Sr₂Ca₂Cu₃O₁₀–(γ-Fe₂O₃)_0.01 superconductor tapes prepared by the powder-in-tube technique with sintering time fixed at 50?h has been investigated. The maximum transport critical current density, J_c of 6490?A/cm² at 77?K, was observed at sintering temperature of 845?°C. A further single intermediate rolling step increases J_c to 9560?A/cm². Sintering temperature from 830 to 845?°C increases the 2223 phase content and resulted in improved J_c. At 850?°C, the content of 2223 phase decreased resulting in a corresponding decrease in J_c. X-ray diffraction patterns suggest that the 2212 phase reacts with non-superconducting phase such as CaCuO₂, (SrCa)₂CuO₃, CaO, and CuO to form the 2223 phase. Samples without γ-Fe₂O₃ prepared under the same condition showed a lower J_c with maximum at 1560?A/cm². Our results show that nanomagnetic γ-Fe₂O₃ addition improved J_c which supports previous calculations on the possibility of frozen flux superconductor with nanomagnetic addition in this class of materials.