Metallurgical Studies and Optimization of Critical Current Density in Bi–(Pb)–Sr–Ca–Cu–O Superconductors

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The Bi–(Pb)–Sr–Ca–Cu–O superconductor has been fabricated into tapes without a sheath and into multifilamentary wires and tapes with a Ag sheath. Superconducting properties, workability, the possibility of forming the superconducting phase in a long wire, morphology, effects of compacting and effects of $c$-axis alignment, to name a few, have been studied. Tape specimens prepared by combination and repetition of cold work (or cold press) and sintering showed a critical current density, $J_{\text{c}}$, as high as $5\times 10^{3}$ A/cm2 at 77 K with good reproducibility and reliability, although these specimens are sufficiently thick (0.5–1.0 mm). (Generally, $J_{\text{c}}$, at the zero field is inversely proportional to thickness.) For these tape specimens (with Cu sheath), sintering and $J_{\text{c}}$ measurement were performed after the Cu sheath was removed. X-ray analysis showed that most of these tape specimens consisted purely of the high-$T_{\text{c}}$ phase ($\sim 107$ K). In these specimens, the $c$ axis tended to align well. This $c$ axis alignment may be a reason for the enhancement in $J_{\text{c}}$. On the other hand, the tape specimens cold-worked and sintered only once showed $J_{\text{c}}$ as small as 102 A/cm2 the $c$ axis showing no sign of the c axis alignment. A 1330-filament Bi–Pb–Sr–Ca–Cu–O wire with a Ag sheath has been successfully fabricated. This multifilamentary wire shows a critical temperature, $T_{\text{c}}$ of $\sim 105$ K. A multifilamentary tape specimen fabricated by a combination of cold working and sintering showed a $J_{\text{c}}$ of $1.05\times 10^{3}$ A/cm2 at 77 K.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
1989-07-20

Metallurgical Studies and Optimization of Critical Current Density in Bi–(Pb)–Sr–Ca–Cu–O Superconductors

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