The effect of lead content on the critical current density, irreversibility field, and microstructure of Ag-clad Bi1.8PbxSr2Ca2Cu3Oy tapes

Abstract

We studied the effect of lead content (x = 0.20−0.40) on the critical current density Jc (0 T, 77 K), irreversibility field H* (77 K), and microstructure of monocore, Ag-clad Bi1.8PbxSr2Ca2Cu3Oy (2223) tapes, finding that tapes with lower lead contents (x = 0.20–0.25) required higher processing temperatures (840 and 832 °C, respectively) to complete 2223 formation, as compared to the optimum 820 °C reaction temperature of the x = 0.30–0.40 tapes. We found that both the zero-field and the in-field properties correlated strongly to the phase purity with Jc (0 T, 77 K) reaching a maximum of ˜20 kA/cm2 for x = 0.30, and then decreasing with increasing lead content to ˜12 kA/cm2 for x = 0.40. H* (77 K) increased from ˜165 mT at x = 0.20 to ˜265 mT at x = 0.30, then declined to 195 mT at x = 0.40. Optimizing the lead content at x = 0.30 maximized both the connectivity and the flux pinning contributions to the critical current density.