Transport Critical Current Density of Ag-Sheathed Bi-Sr-Ca-Cu-O Multifilament Superconductor Tapes with Magnetic Nanopowders γ-Fe_2O_3

摘要

The transport critical current density of multifilament Ag/Bi-Sr-Ca-Cu-O tapes with the addition of magnetic nanopowder (γ-Fe_2O_3) has been measured. The tapes were prepared using the powder in tube method with 30 filaments. Three types of Bi-Sr-Ca-Cu-O starting materials namely from solid state reaction without γ-Fe_2O_3, solid state reaction with y-Fe_2O_3 addition and ultrafine powders prepared by coprecipitation method with y-Fe_2O_3 have been used. The starting composition of the γ-Fe_2O_3 added samples is Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_10-(γ-Fe_2O_3)0.01. The first intermediate rolling enhances J_c but subsequent rolling shows no improvement in J_c. Tapes prepared from coprecipitation powders with γ-Fe_2O_3 added showed the highest J_c of 7890 A/cm~2 at 77 K and in self-field after the first intermediate rolling. These results suggest that intermediate rolling and magnetic nanopowders can be used to improve the critical current density of multifilament Ag/Bi-Sr-Ca-Cu-O superconductor tapes.