THE SYNTHESIS AND CHARACTERIZATION OF TL2BA2CA2CU3O10AGY ESS-THAN-OR-EQUAL-TO-Y-LESS-THAN-OR-EQUAL-TO-0.65) TAPES AND THE AG-INDUCED EFFECTON THEIR MICROSTRUCTURE

The present study is based on improving the intergranular connectivity of TI HTSC tapes by passivation of grain boundaries through the addit ion of silver. TI2Ba2Ca2Cu3O10 HTSC tapes to which silver had been add ed were fabricated by the diffusion of TI 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 TI:2223 as the majorit y phase were found to possess T-c(R = 0) in the range 107-113 K. The c ritical current density (J(c)) of the TI HTSC tapes was found to scale with the silver content and optimum J(c) similar to 9.55 x 10(4) A cm (-2) (20 K) and 7.05 x 10(4) A cm(-2) (77 K) were obtained for TI2Ba2C a2Cu3O10Ag0.40, HTSC tapes. SEM of pure (without silver) and Ag-admixe d TI:2223 tapes revealed that, as the silver content increased, the gr ain size and intergranular connectivity increased. With an optimum con centration of Ag (y = 0.40), a well-oriented platelet-like grain struc ture became stabilized, leading to an improvement in J(c). The most cu rious microstructural feature, observed for the first time in the pres ent study, was the occurrence of sequential layer growth features rese mbling spiral characteristics. The influence of these microstructural features on the superconducting properties, in particular the transpor t critical current density, is described and discussed.