The magnetic field and temperature dependent transport critical current density of Hg-Pb-Bi-Ca-Cu-O ceramic compounds

Mercury-based, ceramic superconductors have been prepared by powder metallu rgy, utilizing a technique of direct synthesis from the oxide powders, The tetragonal Hg-1223 phase was prepared and stabilized over a range of Pb and BiPb compositions, The most interesting material had an onset superconduct ing transition temperature of approximately 133 K. Critical current densiti es were obtained directly from transport measurements and indirectly from m agnetization measurements. The transport critical current densities were or ders of magnitude smaller than the intra-grain critical current densities. The data suggest that the transport critical current is limited by weak cou pling between the grains, and that the intra-grain critical current densiti es deteriorate rapidly above 20K.