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

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 J _c as well. The single-filament and multifilament 2212 tapes have J_c ≳ 5 × 10⁴ A/cm² and J_c ≳ 1.5 × 10⁴ A/cm² at 20 T, respectively. Each material shows a similar dependence of J_c 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.