The effects of stoichiometry in the (Tl,Pb)/sub 1/(Sr,Ba)/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ system on the transport properties of Ag-clad tapes

Evidence shows that texturing is necessary to achieve high current densities 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 powders can lead to enhanced melt-phase formation at lower processing temperatures. An experimental matrix was designed with variations in the Tl/Pb ratio, the total Tl/Pb content, and the Ca/Cu level to change liquid 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 processed by conventional furnace annealing. We report here on the transport properties of these tapes, their strong link behavior, and microstructural development.<>