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

The effect of sintering temperature on the transport properties of Ag-sheathed-(Bi1.6Pb0.4)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, Jc of 6490 A/cm2 at 77 K, was observed at sintering temperature of 845 °C. A further single intermediate rolling step increases Jc to 9560 A/cm2. Sintering temperature from 830 to 845 °C increases the 2223 phase content and resulted in improved Jc. At 850 °C, the content of 2223 phase decreased resulting in a corresponding decrease in Jc. 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 Jc with maximum at 1560 A/cm2. Our results show that nanomagnetic γ-Fe2O3 addition improved Jc which supports previous calculations on the possibility of frozen flux superconductor with nanomagnetic addition in this class of materials.