S. Yamade

DI-BSCCO wire with Ic over 200 A at 77 K

The highest Ic of a latest DI-BSCCO® tape, which is the high performance silver sheathed Bi2223 tapes produced with CT-OP® technique, has reached 210 A (500A/cm-width) at 77K, self-field. The wide-range measurement of Ic using temperature variable system also has proved the highest performance at each temperature and external magnetic field. The combination of CT-OP® and stainless steel lamination techniques has concurrently obtained Ic higher than 200 A, rated tensile stress more than 300 MPa and rated tensile strain more than 0.4 % at 77 K. A texture analysis using synchrotron radiation has revealed explicit correlation between Jc and c-axis misalignment angle in CT-OP® processed tapes.

Recent Progress in High Performance Ag-Sheathed Bi2223 Wire (DI-BSCCO®)

Sumitomo Electric has been developing the silver-sheathed Bi2223 multi-filamentary wires since the discovery of Bi-based superconductors. DI-BSCCO is the high performance wires produced using the controlled-overpressure (CT-OP) sintering technique. The present commercial DI-BSCCO can provide the uniform high critical current, Ic, up to 180 A with length over 2000 m, and recently 200 A were succeeded to be obtained by the same kind of 1000 m length wires, resulting from the improvement and control of the microstructure in Bi2223 multi-filaments. The short trial wires of several meters have exhibited the highest Ic over 240 A at 77K in self-field (corresponding to 580 A per 1 cm-width). Besides, the optimization of carrier density after CT-OP led to further enhancement of Ic, reached 250 A. All the derivative products also have uniform critical current properties over entire length even after lamination with the reinforcing metals. The performances of DI-BSCCO can meet the growing needs for various application of high temperature superconductor like high in-field applications, such as magnets and motors. The recent progress in transport properties of commercial DI-BSCCO and R&D short trial wires is shown.

Limiting current mechanisms of Bi2223 wires in magnetic fields

Controlled overpressure (CT-OP) processing eliminates pores and heals cracks, which densifies the Bi2223 filaments and increases the critical current of Ag-sheathed Bi2223 wire. High current capacity wires with critical current values around 210 A at 77 K and self-field have been achieved. The enhancement of the current capacity seems to be due to reducing the weak links between Bi2223 grains and improving the flux pinning. In order to understand the mechanisms for transport critical current in Bi2223 wires, the dependence of the critical current on magnetic field and temperature has been investigated. The critical current is measured as a function of the perpendicular and parallel magnetic fields, up to 12 T, at temperatures ranging from 4.2 to 90 K. These results indicate that higher critical current is associated with highly textured and well connected Bi2223 grains. To further improve a critical current of Bi2223 wires, it is necessary to decrease the misalignment angle and reduce the fraction of Bi2212 and secondary phases.

Progress in high performance DI‐BSCCO wire

The high performances of Dynamically Innovative BSCCO (DI‐BSCCO) wire have been reviewed. Critical current (Ic) has reached 210 A (77 K and self‐field), which is equivalent 500 A per 10 mm width, by total optimization of whole manufacturing process including Controlled Over Pressure (CT‐OP) sintering. The further higher Ic value will be available on preferable oxide filaments with the improved c‐axis orientation of Bi2223 grains, the minimized non‐superconducting phases, and so on. The Ic of long length wires has been reached 203 A of 42 m 180 A of 1,400 m. Ic in the magnetic field at low temperature has showed great improvements in comparison with the past 150 A class wire. The mechanical performances has been improved due to the densification of the Bi2223 filaments up to 100% by CT‐OP process, moreover have been dynamically improved by reinforcement with stainless steel tapes or brass tapes. These results can enable DI‐BSCCO wire to be applied for the cryogenic applications such as motors, magnets, cables and so on.The high performances of Dynamically Innovative BSCCO (DI‐BSCCO) wire have been reviewed. Critical current (Ic) has reached 210 A (77 K and self‐field), which is equivalent 500 A per 10 mm width, by total optimization of whole manufacturing process including Controlled Over Pressure (CT‐OP) sintering. The further higher Ic value will be available on preferable oxide filaments with the improved c‐axis orientation of Bi2223 grains, the minimized non‐superconducting phases, and so on. The Ic of long length wires has been reached 203 A of 42 m 180 A of 1,400 m. Ic in the magnetic field at low temperature has showed great improvements in comparison with the past 150 A class wire. The mechanical performances has been improved due to the densification of the Bi2223 filaments up to 100% by CT‐OP process, moreover have been dynamically improved by reinforcement with stainless steel tapes or brass tapes. These results can enable DI‐BSCCO wire to be applied for the cryogenic applications such as motors, magnets, cab...

Improved critical current density in DI-BSCCO

High Ic in DI-BSCCO has been demonstrated even in high temperature up to 90K and parallel magnetic field up to 200 mT. This performance is advantageous especially to power cables cooled with pressurized liquid nitrogen, where current and temperature fluctuates in real operation. Recent development has updated the highest Jc at 77K, self-field to 630 A/mm2 in a R&D tape. The evaluation by a scanning magnetic microscope has demonstrated the highest Jc of 900 A/mm2 at the midst of a tape which has Ic of 200 A. This property promises innovative Ic more than 300 A in future DI-BSCCO.