Effects of precursor powder particle size on the powder-in-tube Ba1−xKxFe2As2 superconducting tapes

Abstract

In this paper, we studied the effects of precursor powder particle size on Ag-sheathed powder-in-tube Ba1−xKxFe2As2 (Ba-122) superconducting tapes. Precursor powders with different particle sizes were prepared by changing the grinding time of calcined bulks. We systematically investigated the relationship between particle size of precursor powder, microstructure and superconducting properties of tapes. For short grinding time, the uneven particle size distribution damages the interface between Ba-122 core and Ag sheath, resulting in distinct sausage effect and decline of mass density of the Ba-122 core, causing severe fluctuation for the transport current density (J c). Then with the extension of grinding time, the transport J c becomes more uniform due to the improved homogeneity but lower with the reduction of average particle size from 21.5 to 9.5 μm. The J c of samples made with precursor powders by grinding 20 min reaches 5 × 104 A cm−2 at 4.2 K and 10 T. It has been shown that the coarse grains are easier to align along the rolling direction of tapes and lead to a higher degree of c-axis texture. Our results demonstrated the importance of controlling the homogeneity and particle size of precursor powders in achieving superior J c for iron-based superconducting tapes.