THE EFFECTS OF STOICHIOMETRY IN THE (TL,PB)(1)(SR,BA)(2)CA2CU3OX SYSTEM ON THE TRANSPORT-PROPERTIES OF AG-CLAD TAPES

Evidence shows that texturing is necessary to achieve high current den sities and strong links in the Tl-based superconductors. Conventional sintering is not sufficient to achieve strong links, but instead, melt processing is required to produce platelets which can develop into a textured structure. Changes in the stoichiometry of the precursor powd ers can lead to enhanced melt-phase formation at lower processing temp eratures. An experimental matrix was designed with variations in the T l/Pb ratio, the total Tl/Pb content, and the Ca/Cu level to change liq uid formation and subsequent grain growth. Thirteen compositions were prepared in both pellet form and as Ag-clad tapes to investigate grain development over a range of thermal processing conditions. Tapes were produced using unreacted powders by the powder-in-tube method and pro cessed by conventional furnace annealing. We report here on the transp ort properties of these tapes, their strong link behavior, and microst ructural development.