Advances in processing, characterizing and applications of Bi-based superconductors

Advances in the processing and fabrication of high critical current density (J/sub c/) long length conductors, Silver sheathed superconducting, wires, superconducting magnets and coils from silver sheathed Bi-2223 tapes, pancake coil magnets from one to ten mater length and mono multi filament Bi-222/ 2212 high critical temperature superconductors by powder in tube technique continue to bring these materials closer to commercial applications. Consistently J/sub c) great r than 104 A/cm/sup 2/ have been achieved along the entire length of a 1.260 m long, 37 filament B-2223 tape. investigations of rare earth and oxide compounds have yielded several new classes of exotic superconductors. These include magnetically ordered superconductors, A15 superconductors, buckyball superconductors and high Tc oxide superconductors. These materials have properties significantly different from those of conventional superconductors. The Bi/sub 17/Pb/sub 0.3/Sr/sub 2/Ca/sub 2-x/R/sub x/Cu/sub 3/O/sub y/ (R = Gd, Sm) system is investigated for different concentration of x (1-5 at. %). X-ray diffraction, electrical resistance and kinetic studies are performed to investigate the changes in superconducting properties. X-ray diffraction results reveal that volume fraction of high T/sub c/ 2223 phase that is present in the samples without Gd/sup 3+/ (x=0 ) vanishes even for x = 0.01. The de resistivity results indicates that the Gd/sup +3/ substitution converts the 223 phase in to the 2212 phase. Activation energies and frequency factors for crystallization were determined by non isothermal differential analysis, employing different models. The results are discussed on the basis of a possible variation of hole concentration with trivalent rare earth ion substitution and on the basis of magnetic nature of substitute ions. (author)