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 of MxPb0.4Sr1.6Ba0.4Ca2Cu3O8+delta {M: T1 (0.32 less than or equal to x less than or equal to 0.74) or Hg (0.18 less than or equal to x less than or equal to 0.68)} have been studied by magnetization and transport measurements. For T1-1223 we have found the optimum T1 doping level to be x = 0.53 regarding the grain properties, the content of superconducting phase, the first penetration field H-pl(wl), the transport (J(c)(tr)), magnetic intergrain (J(c)(M)) and intragrain (J(c)(g)) critical current densities. The critical temperature T-c of the as-sintered T1-1223 sample decreased with increasing TI content. Post-annealing in oxygen improved the T-c for Tl contents of x greater than or equal to 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. (C) 1999 Elsevier Science B.V. All rights reserved.