Development of novel superconducting wires and tapes with high critical current densities at liquid nitrogen temperature

In order to develop the superconducting wires and cables applicable at liquid nitrogen temperature in magnetic fields for next generation, we have studied basic critical current properties of newly found Re-doped Hg-based superconductors and attempted the synthesis of their grain-aligned tapes. The best tape exhibited zero resistance over 50 k Oe at 77 K, which is the record-high irreversibility field as for superconducting tapes. On the other hand, heavily Pb-doped Bi2212 superconductor was discovered to show dramatically improved critical current properties compared to the pure Bi2212. Pb-doping was found to essentially decrease the electromagnetic anisotropy resulting in a enhancement of pining strength up to high temperatures in the present system. It was suggested that the Bi(Pb) 2212 can be a promising candidate material for practical application at 40-50 K for high field generation. (author)