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-(gamma-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/cm(2) at 77 K, was observed at sintering temperature of 845 degrees C. A further single intermediate rolling step 2 increases J(c), to 9560 A/cm(2). Sintering temperature from 830 to 845 degrees C increases the 2223 phase content and resulted in improved J(c). At 850 degrees 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)(2)CuO3, CaO, and CuO to form the 2223 phase. Samples without gamma-Fe2O3 prepared under the same condition showed a lower J(c), with maximum at 1560 A/cm(2) . Our results show that nanomagnetic gamma-Fe2O3 addition improved J(c) which supports previous calculations on the possibility of frozen flux superconductor with nanomagnetic addition in this class of materials. (c) 2005 Elsevier Ltd. All rights reserved.