Ryosuke Hata

DI-BSCCO wires by Controlled over pressure sintering

Sumitomo Electric successfully developed drastically innovative Bi-2223 (DIBSCCO), namely, commercially produced Bi2223 long length wires using the controlled over pressure sintering (CT-OP) with unique properties quite different from conventional silver sheathed BSCCO wires. CT-OP prevented pores occurring in BSCCO cores, so it reformed conventional Bi2223 wires to DI-BSCCO with excellent properties of higher critical currents, stronger mechanical strength and better durability against temperature rise in cryogen such as pressurized liquid nitrogen. It enhanced the critical current by 50 percent conventional wires sintered in normal atmospheres. Critical tensile stress was also improved by more than 150 percent. Any ballooning defects and degradation of critical current, one of the critical problems for the conventional BSCCO wires, were not found in full length of several km long DI-BSCCO tapes after 24 hours immersion into 1MPa liquid nitrogen.

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.

Controlled Overpressure Processed Bi2223 Wires for Power Applications

Progress in the performance of the controlled overpressure (CT‐OP) processed (Bi,Pb)2Sr2Ca2Cu3Ox (Bi2223) wire is reviewed. Optimization of the CT‐OP processing improved microstructure of Bi2223 wires and increased their critical current (Ic) by greater than 60% compared to normal pressure processing. The CT‐OP processing effectively removed pores and cracks. The SEM show CT‐OP wires had very dense, uniform, and well connected Bi2223 grain. Densification of the CT‐OP wires prevents liquid nitrogen penetration during long term exposure to liquid nitrogen of them for use in power cable applications. Ballooning caused by trapped nitrogen, that expands when warming up to room temperature, doesn’t occur in CT‐OP wires. These high performance levels in CT‐OP wires have enabled commercial level applications such as power cables, magnets and motors.

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...