TEM investigation of the microstructure and properties of Tl(Bi)-1223/Ag powder-in-tube superconducting tapes

摘要

We have made a detailed study of the microstructure of (Tl0.78Bi0.22) (Sr1.6Ba0.4)Ca2Cu3Ox/Ag (Tl(Bi)-1223/Ag) powder-in-tube superconducting tapes using transmission electron microscopy. Melt processing led to a markedly different microstructure compared to that obtained from more conventional primarily solid state reaction routes. Clusters of well connected grains were observed resulting in a denser and more uniform microstructure. This is consistent with an improvement in the magnetic field dependence of the critical current density (J(c)) for the melt processed tapes with reduced degradation of J(c) in field and an increase in the high-field J(c) plateau. In addition, the magnetic screening currents flow on a scale of the same order of magnitude as the grain clusters. The Ag/Tl(Bi)-1223 interface wits also studied and Tl(Bi)-1223 was shown to align preferentially on a flat Ag surface with the (001)(Tl-1223) planes parallel to the interface. The morphology of the Ag surface is often too rough to maintain the alignment along the interface and as a result, no long-range texture is observed. [References: 29]