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Intrinsic defect structures of polycrystalline CaKFe4As4 superconductors

Authors :
Yoshiyuki Yoshida
Taichiro Nishio
Akira Iyo
Yoshihisa Kamiya
Hiroshi Eisaki
Shigeyuki Ishida
Keiichi Yanagisawa
Kenji Kawashima
Yoshinori Tsuchiya
Hiraku Ogino
Koji Kimoto
Pavan Kumar Naik Sugali
Source :
Physical Chemistry Chemical Physics. 23:19827-19833
Publication Year :
2021
Publisher :
Royal Society of Chemistry (RSC), 2021.

Abstract

We investigated the defect structures of polycrystalline CaKFe4As4 (CaK1144) superconductors by scanning transmission electron microscopy (STEM). The STEM studies revealed the presence of a one-layer CaFe2As2 (∼1 nm size) defect along the ab-plane, as observed in single crystalline CaK1144. Step-like CaFe2As2 defects are also observed. These nanoscale defects generate fine-sized stacking faults, a lattice mismatch, and stress field defects in the matrix of CaK1144 owing to the different sizes. Correlation of the defects in polycrystalline and single crystalline samples suggests that the defects type and their density depend on the synthesis conditions. A self-field critical current density (Jc) of 15.2 kA cm−2 was obtained at 5 K, and the curves were sustained above 30 K with a considerable Jc value of 1.4 kA cm−2. We investigated the relationship between the observed intrinsic defects and the behavior of the field dependence of Jc. The intrinsically intergrown planar defects, even in polycrystalline samples, are expected to be advantageous for various high-field applications of bulk CaK1144 superconductors.

Details

ISSN :
14639084 and 14639076
Volume :
23
Database :
OpenAIRE
Journal :
Physical Chemistry Chemical Physics
Accession number :
edsair.doi...........882a4a62bb4d7e30d78d3bb7b4c3aa28
Full Text :
https://doi.org/10.1039/d1cp02613e