High Quality Bi-2212 Tapes Prepared by Oxidation of Metallic Precursors

Aiming at manufacturing long lengths of Bi-2212 tapes, we have developed a technique of synthesis by oxidation of metallic precursors. This technique is based on the sequential electrodeposition of the constituting metals (Cu, Bi, Ca and Sr) onto polycrystalline silver tapes, followed by oxidation at temperatures in the interval 800–880 °C. The deposition sequence as well as the thermal treatments have been optimized using the results of a complete microstructural characterisation made by optical and scanning electron microscopy, X-ray diffraction, electron probe microanalysis as well as DTA and TGA analysis. As a result, highly textured tapes, a few microns thick, have been obtained. The resistive transition of the optimized specimens is quite sharp, of the order of 2 K, measured with a direct current density of 500 A/cm2. Transport critical current densities Jc = 15,000 A/cm2 have been obtained at 77 K on specimens with a Tc(offset) = 82 K. From magnetic measurements (Bean model) a Jc of 106 A/cm2 has been found at 4 K.