Advantageous grain boundaries in iron pnictide superconductors

TL;DR

This study demonstrates that iron pnictide superconductors exhibit superior grain boundary properties compared to cuprates, maintaining high critical current densities at larger misorientation angles, which could improve superconducting wire fabrication.

Contribution

It reveals that iron pnictide superconductors have a higher critical angle for grain boundary misorientation, reducing current decay and offering advantages over cuprates.

Findings

JcBGB remains high (>1 MA/cm2) up to ~9° misorientation angle

Decay of JcBGB is smaller than in YBCO at angles above the critical angle

Iron pnictides have better grain boundary tolerance than cuprates

Abstract

High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries-the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here, we report that High critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (thetaGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (> 1 MA/cm2) and nearly constant up to a critical angle thetac of ~9o, which is substantially larger than the thetac of ~5o for YBCO. Even at thetaGB > thetac, the decay of JcBGB was much smaller than that of YBCO.