The synthesis and characterization of tapes and the Ag-induced effect on their microstructure

Abstract

The present study is based on improving the intergranular connectivity of Tl HTSC tapes by passivation of grain boundaries through the addition of silver. HTSC tapes to which silver had been added were fabricated by the diffusion of Tl vapour in the precursor tape to which silver had been added. The tapes were cast by using a doctor-blade tape-casting machine. These tapes having Tl:2223 as the majority phase were found to possess in the range 107 - 113 K. The critical current density of the Tl HTSC tapes was found to scale with the silver content and optimum (20 K) and (77 K) were obtained for HTSC tapes. SEM of pure (without silver) and Ag-admixed Tl:2223 tapes revealed that, as the silver content increased, the grain size and intergranular connectivity increased. With an optimum concentration of Ag (y = 0.40), a well-oriented platelet-like grain structure became stabilized, leading to an improvement in . The most curious microstructural feature, observed for the first time in the present study, was the occurrence of sequential layer growth features resembling spiral characteristics. The influence of these microstructural features on the superconducting properties, in particular the transport critical current density, is described and discussed.