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 metallurgy, 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 superconducting transition temperature of approximately 133 K. Critical current densities were obtained directly from transport measurements and indirectly from magnetization measurements, The transport critical current densities were orders of magnitude smaller than the intra-grain critical current densities. The data suggest that the transport critical current is limited by weak coupling between the grains, and that the intra-grain critical current densities deteriorate rapidly above 20 K.