Comparison of Bi-system 2223 and 2212 thick superconducting tapes: Grain alignment, current density, and strain effects

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Abstract
Bi‐Sr‐Ca‐Cu‐O (2212) and Bi‐Pb‐Sr‐Ca‐Cu‐O (2223) superconductors were fabricated into silver‐sheathed tapes by cold rolling and sintering. The resulting samples are compared in terms of microstructural alignment, critical current density, and strain dependence. Although both samples show good grain alignment, that of the 2212 phase is superior due to partial melting during heat treatment. This microstructural superiority is reflected in superior Jc as well. The single‐filament and multifilament 2212 tapes have Jc ≳ 5 × 104 A/cm2 and Jc ≳ 1.5 × 104 A/cm2 at 20 T, respectively. Each material shows a similar dependence of Jc upon strain, with the 2223 phase exhibiting slightly more degradation. Furthermore, multifilamentary tapes were less affected by strain than single‐filament tapes. A multifilamentary tape at 4.2 K, 0.5 T showed only a weak dependence upon strain, indicating that the strain dependence of the Bi system at low temperature may not be severe.