THE SYNTHESIS AND CHARACTERIZATION OF TL2BA2CA2CU3O10AGY (0.10-LESS-THAN-OR-EQUAL-TO-Y-LESS-THAN-OR-EQUAL-TO-0.65) TAPES AND THE AG-INDUCED EFFECT ON THEIR MICROSTRUCTURE

摘要

The present study is based on improving the intergranular connectivity of TI HTSC tapes by passivation of grain boundaries through the addition of silver. TI2Ba2Ca2Cu3O10 HTSC tapes to which silver had been added 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 majority phase were found to possess T-c(R = 0) in the range 107-113 K. The critical 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 TI2Ba2Ca2Cu3O10Ag0.40, HTSC tapes. SEM of pure (without silver) and Ag-admixed TI: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 J(c). 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. [References: 23]