Critical current density (J
c) and its dependence on magnetic field in Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting wire was improved by grain alignment and homogenization of the high-T
c phase (110 K). The maximum transport current density at 77.3 K in a zero magnetic field was increased to 6930 A/cm2. The magnetic field dependence of J
c (0.1 µV/cm criterion) was summarized as follows: 1660 A/cm2 (I ⊥H, a-b plane ∥H, 0.1 T), 900 A/cm2 (I ⊥H, a-b plane ⊥H, 0.1 T). We found that the grain boundaries were bonded strongly in the direction of alignment.
The critical current density (J
c) in Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting wire increased to 17,400 A/cm2 in a zero magnetic field. The magnetic field dependence of J
c was improved according to the increase of J
c in a zero magnetic field. Fine, dispersed, nonsuperconducting phases were observed through SEM and TEM. These phases are expected to act as pinning sites.
Superconducting wires of Y–Ba–Cu–O system have been investigated. Wires were fabricated by powder method. The wires were successfully reduced to a small diameter. Wires of Y1Ba2Cu3O7 exhibit zero resistance at 90 K.
Samples of Ba2Y(Cu, Ti)3O
y
oxide were synthesized and the effect of substituting Cu with Ti was studied. In the Ba2Y(Cu3-x
Ti
x
)O
y
(0≦x≦0.9), specimens were obtained which indicated a T
c of over 80 K. In the composition BaαYCuβTi0.6O
y
(1.9≦α≦2.3, 2.3≦β≦3.5), some (Cu Ti)-rich samples indicated a T
c of over 95 K which was as high as that of the existing Ba2YCu3O
y
. Diamagnetic signals measured by AC susceptibility at room temperature were detected in some specimens. Zero electric resistance was observed (<10-4 Ωcm at our experimental resolution) up to 300 K in the composition Ba2YCu2.4Ti0.6O
y
sintered at 940°C.
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