The formation of defects and their influence on inter- and intra-granular current in sintered polycrystalline 122 phase Fe-based superconductors. (1st July 2019)

• Record Type: Journal Article
• Authors: Shimada, Yusuke; Yamamoto, Akiyasu; Hayashi, Yujiro; Kishio, Kohji; Shimoyama, Jun-ichi; Hata, Satoshi; Konno, Toyohiko J
• Is Part Of: Superconductor science & technology. Volume 32:Number 8(2019:Aug.)
• Publication Date: 2019-07-01
• Subjects: Fe-based superconductor -- electromagnetic properties -- multi-scale grain structure -- electron microscopy; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/ab0eb6
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: The evolution of intra- and inter-granular structures in Co-doped BaFe2 As2 (Ba-122) has been studied to address key issues associated with limited inter-granular current transport in randomly oriented polycrystalline Fe-based superconducting materials. We found that the following phenomena occur with an increase in reaction temperature: (i) significant grain growth; (ii) formation and evolution of two types of cracks; (iii) enhancement in the intra-granular current loop; (iv) reduction of magnetic shielding volume; and (v) decrease of the inter-granular transport current. A strong correlation between the inverse grain size and the inter-granular current density was observed. These results indicate that the key microstructural feature to achieve high transport current is a small grain size with no inter-granular cracks, and that low temperature synthesis is an effective path to this end. Based on the observed stacking faults and inter-granular amorphous layers, we propose a model for the formation of the two types of cracks in a polycrystalline Ba-122 phase, i.e. intra- and inter-granular cracks.