Critical current of highly textured Bi 2212 tapes

Abstract

Highly textured tapes, a few microns thick, of Bi 2212 high T c superconductor have been prepared by oxidation of metallic precursors electrolytically deposited onto polycrystalline silver ribbons. The microstructure of the specimens has been characterised by optical and scanning electron microscopy, X-ray diffraction and electron microprobe analysis. The resistive transition of optimized specimens was found to be very sharp and to broaden very slowly with increasing current density. T c has been always recorded with a current density of 500 A/cm 2. Critical current densities J c = 15 000 A/cm 2 have been measured at 77 K on specimens having an offset T c= 82 K. These values correspond to measurements performed with direct current. Magnetic measurements of J c as a function of temperature have been performed between 4 and 77 K, and the effect of magnetic fields // c, up to 6 tesla, on these current densities has been determined. At 4 K and 0 tesla a J c = 10 6A/cm 2 has been obtained and a current density as high as 3 10 5A/cm 2 still remained at 6 tesla.