Behavior of Critical Current Density and Grain Misalignment of Hot-Pressed Bi-2223 Bar Current Leads

Abstract

Bi-2223 bar current leads were fabricated by a combination of cold isostatic pressing (CIP) and hot pressing (HP). The critical currents were measured at 77 K by varying external dc magnetic field (B), which was applied parallel and perpendicular to the bulk sample surface, i.e., I _c (B//bar surface) and I _c (B ⊥ bar surface), respectively. The critical current I _c and critical current density J _c were 119 A and 300 A/cm², respectively, for the bar current lead of 0.4 cm thick, 1.0 cm wide, and 5.4 cm long. The effective grain misalignment angle, ϕ_eff, was around 10°, calculated from its I _c (B//bar surface) and I _c (B ⊥ bar surface) curves by using 2D model. For comparison, the average grain misalignment angle, ϕ_av, found in microstructure using SEM, was measured by pole figure. The obtained results were in agreement with the effective grain misalignment angle ϕ_eff. The phases and microstructure were analyzed by XRD and SEM.