Bi-based high temperature superconducting tapes by cold rolling method

Abstract

Bi-based high-temperature superconductor doped by lead with and without silver addition was used to produce tape approximately 1.2-cm wide and up to 20-cm long. Powder was calcined at 800 degrees C, 810 degrees C, and 835 degrees C for 50 h each time and loaded into silver tubes with o.d.=6.35 mm and i.d.=4.35 mm. Tapes with nominal thicknesses of 0.5 mm, 0.35 mm, and 0.2 mm were produced by the cold rolling technique. Direct transport current, DC magnetization, and AC susceptibility measurements were performed to characterize the superconducting properties of the tapes. The authors observed a significant increase in the magnetization critical current density with increasing number of calcinations and decreasing thickness of the tape, which is equivalent to the introduction of deformations into the system, thus increasing the number of pinning centers. A silver addition (3 wt.%) increases connectivity between grains and creates much cleaner grain boundaries.