Influence of the Tl- and Hg-content on magnetic and transport properties of the Pb, Sr-doped Tl-1223 and Hg-1223 superconductors

The effects of the thallium and mercury content x on the as-sintered and post annealed samples MxPb0.4Sr1.6Ba0.4Ca2Cu3O8+d { M: Tl (0.32 <= x <= 0.74) or Hg (0.18 <= x <= 0.68) } have been studied by magnetization and transport measurements. For Tl-1223 we have found the optimum Tl doping level to be x = 0.53 regarding the grain properties, the content of superconducting phase, the first penetration field , the transport ( ), magnetic intergrain ( ) and intragrain ( ) critical current densities. The critical temperature Tc of the as-sintered Tl-1223 sample decreased with increasing Tl content. Post-annealing in oxygen improved the Tc for Tl contents of x ? 0.53 and had generally positive effects on the critical current densities. The intergrain properties of the Hg-1223 samples were much worse than those of the Tl-based superconductors.