Calculation of the transport critical current density of c-axis textured 122 iron-based superconductors

TL;DR

This study models the maximum transport critical current density in c-axis textured 122 iron-based superconductors, predicting potential improvements and analyzing factors affecting current flow in polycrystalline tapes.

Contribution

It introduces a 3D flow network model to estimate the maximum critical current density and evaluates the effects of microstructural factors on superconducting performance.

Findings

Maximum super-current could reach 2*105 A/cm2 in ideal conditions.

Over 30% of grain boundaries may hinder current flow.

Optimal grain shape enhances transport Jc in textured tapes.

Abstract

The c-axis textured Sr1-xKxFe2As2 tapes produced by cold rolling and post-annealing, could carry a high super-current over 2*104 A/cm2. However, the magnitude is far from its maximum, because of the current obstacles associated with various defects in the material. To predict the maximal transport critical current density, we modeled the current paths in a c-axis textured polycrystal as a three-dimensional flow network, and calculated the maximum flow with the Ford-Fulkerson algorithm. It indicates that a much higher super-current of about 2*105 A/cm2 could be achieved in an ideal c-axis textured K-doped 122 polycrystal. The dependences of transport Jc on density, content of invalid boundary and grain size and shape were also studied. The results imply that, over 30% of the grain boundaries in the reported c-axis textured Sr1-xKxFe2As2 tapes may act as current obstacles, and the large ratio of width to thickness was expected to be the most favorable grain shape for high transport Jc in c-axis textured 122 superconducting tapes.