The growth process of the (2223) phase in Bi-Sr-Ca-Cu-O has been studied for oxides with nominal composition Bi2Pb0.6Sr2Ca2Cu3O x prepared by sintering at 835∼855°C for 5∼160 h in air. The partial melting which starts to occur at T pm≃842°C enhances the growth rate of the (2223) phase and produces a nearly single phase within 40 h. However, it causes a disturbance in current paths and suppresses the value of T c(ρ=0) below 100 K. The sample which has the highest T c(ρ=0) and the nearly single (2223) phase is obtained by sintering at a temperature just below T pm for a long period of time.

The effect of Pb addition on superconductivity was studied on the systems with nominal compositions (BiPb x )2Sr2Ca2Cu3O y , (Bi1-x Pb x )2Sr2Ca2Cu3O y and (Bi1-x Pb x )2Sr2Ca2Cu3.6O y . The melting point decreases monotonically from ∼880 to ∼860°C as x increases from 0 to 0.45 in the systems, while the volume fraction of the high-T c phase (HTP) and the offset value of T c show a peak around x=0.2∼0.3. Further increase in x produces the Ca2PbO4, leading to the suppression of the HTP. The amount of Pb suitable for the formation of the HTP is limited by the competition between the reaction to form the HTP by the catalytic effect of Pb and the one to form the Ca2PbO4.

Initial magnetization curve M(H) and magnetic relaxation M(t) were studied on the Ag-sheathed and highly c-axis oriented tape of Bi-Pb-Sr-Ca-Cu-O with transport Jct=5400 and 2400 A/cm2 (77 K, H=0). The Jc value, derived from M(H) curve based on Bean’s critical-state model, agrees fairly well with the Jct. The lower critical field Hc1 for H⊥c axis from M(H) curve increases with a slope of −0.2 Oe/K as temperature decreases from Tc, and it approaches the saturated value of 15 Oe at T∼0 K. The magnitude is much lower than that for the high-Tc superconductors La-Sr-Cu-O and Y-Ba-Cu-O. The creep rate and activation energy U0 are evaluated from M(t) based on the flux creep model. The results show a significant dependence on the measuring process and magnetic field H. The U0 at 5 K for H=500 Oe (H⊥c) is 0.4 eV for the in-field magnetization (IN) and 0.1 eV for the remanent magnetization (REM), which are larger than those for Bi-based high-Tc superconductors reported previously. The U0 for the IN shows a peak of 0.8 eV around 30 K and then decreases as temperature increases, while a peak in it is weakened for the REM. The U0 at H=30 Oe (H⊥c) for the IN is one order larger than that for 500 Oe and the peak temperature is shifted to the lower temperature (∼10 K).

The powder-in-tube method using an Ag sheath is applied to achieve high current capacity in the tapes of Bi-Pb-Sr-Ca-Cu-O (BPSCCO) with the high-Tc phase (Tc=110 K), by a combination process of cold working and sintering. Two kinds of the BPSCCO powder with and without Ag doping are used as the materials for tape fabrication. The morphology, structure, and critical current density Jc are investigated on the tapes by x-ray diffraction, differential thermal analysis, scanning electron microscope, magnetic susceptibility, and I-V curves. The optimum sintering conditions to obtain a maximum in the value of Jc at 77 K and 0 T are presented in the Ag-doped tapes and the nondoped ones. An improvement in the Jc vs B properties up to 1 T at 77 K is presented in the BPSCCO tape by Ag doping. The Ag doping causes neither change in the value of Tc (=110 K) nor decomposition of the high-Tc phase.

The powder-in-tube method using an Ag sheath is applied to achieve high current-capacity in the tapes of Bi-Pb-Sr-Ca-Cu-0 (BPSCCO) with the high-Tc phase, by a combination of cold working and sintering. Two kinds of the BPSCCO powders with and Magnetic Susceptibility and I-V characteristics at 77K obtained for above powders are presented and discussed: An improvement in Jc vs B properties of the BPSCCO tapes by Ag doping is presented.