Investigation of src='/images/tex/17128.gif' alt='J_{c}'> -Suppressing Factors in Flat-Rolled src='/images/tex/21850.gif' alt='hbox {Sr}_{0.6}hbox {K}_{0.4}hbox {Fe}_{2}hbox {As}_{2}/hbox {Fe}'> Tapes Via Microstructure Analysis

摘要

Pnictide superconductors will be very promising for applications if wires with high critical current density can allow reel-to-reel large-scale fabrication at low costs. To understand the mechanism(s) that limited in flat-rolled (Sr122) tapes, microstructure analysis has been considered the most direct and efficient way. Here, we report on high-resolution microstructure imaging and analysis on Fe-sheathed flat-rolled Sr122 tapes, which have a as high as at 10 T and 4.2 K. The overlapping nature of the Sr122 plates was clearly observed. Transmission electron microscopy/scanning transmission electron microscopy analysis showed that, besides the cracks formed during the fabrication process, the phase and cavities caused by the inhomogeneously dispersed Sr and K are the other important factors suppressing . The wetting phase FeAs at the grain boundaries can be partially substituted by Sn in Sn-added samples. Our findings provide insights that pave the way to further enhance the critical current of the rolled 122 tapes up to the practical level.