Influence of the microstructure on magnetic-shielding properties of (Bi,Pb)-Sr-Ca-Cu-O superconductor

摘要

Bi-2223 based ceramic magnetic shields were prepared by thermomechanical treatment. It was evidenced that the orientation of the superconducting grains with the c-axis perpendicular to z-axis of the tube is favourable. The single tube of the wall thickness of only 1.8 mm traps a magnetic flux density of 30 mT at 77.3 K and 60 mT at 63.2 K, and the shielding efficiency is substantially increased in coaxially arranged tubes. Thus for the system of five tubes of overall thickness 9.6 mm, B_(tr) reaches 70 mT at 77.3 K.