Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders

Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders

The flux pinning properties of reacted-and-pressed Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> powder were measured using magnetic hysteresis loops in the temperature range 20 K &#8804; <i>T</i> &#8804; 35 K. The sca...

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Main Authors: Michael R. Koblischka, Anjela Koblischka-Veneva, Jörg Schmauch, Masato Murakami
Format: Article
Language:English
Published: MDPI AG 2019-07-01
Series:Materials
Subjects:
iron-based superconductors
critical currents
flux pinning
microstructure
Online Access:https://www.mdpi.com/1996-1944/12/13/2173
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spelling doaj-7abe0659675442018fbded21e8674d982020-11-25T01:42:51ZengMDPI AGMaterials1996-19442019-07-011213217310.3390/ma12132173ma12132173Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> PowdersMichael R. Koblischka0Anjela Koblischka-Veneva1Jörg Schmauch2Masato Murakami3Experimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, GermanyExperimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, GermanyExperimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, GermanySuperconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, Tokyo 135-8548, JapanThe flux pinning properties of reacted-and-pressed Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> powder were measured using magnetic hysteresis loops in the temperature range 20 K &#8804; <i>T</i> &#8804; 35 K. The scaling analysis of the flux pinning forces (<inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>F</mi> <mi>p</mi> </msub> <mo>=</mo> <msub> <mi>j</mi> <mi>c</mi> </msub> <mo>&#215;</mo> <mi>B</mi> </mrow> </semantics> </math> </inline-formula>, with <inline-formula> <math display="inline"> <semantics> <msub> <mi>j</mi> <mi>c</mi> </msub> </semantics> </math> </inline-formula> denoting the critical current density) following the Dew-Hughes model reveals a dominant flux pinning provided by normal-conducting point defects (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>&#948;</mi> <mi>l</mi> </mrow> </semantics> </math> </inline-formula>-pinning) with only small irreversibility fields, <inline-formula> <math display="inline"> <semantics> <msub> <mi>H</mi> <mi>irr</mi> </msub> </semantics> </math> </inline-formula>, ranging between 0.5 T (35 K) and 16 T (20 K). Kramer plots demonstrate a linear behavior above an applied field of 0.6 T. The samples were further characterized by electron backscatter diffraction (EBSD) analysis to elucidate the origin of the flux pinning. We compare our data with results of Weiss et al. (bulks) and Yao et al. (tapes), revealing that the dominant flux pinning in the samples for applications is provided mainly by grain boundary pinning, created by the densification procedures and the mechanical deformation applied.https://www.mdpi.com/1996-1944/12/13/2173iron-based superconductorscritical currentsflux pinningmicrostructure
collection DOAJ
language English
format Article
sources DOAJ
author Michael R. Koblischka
Anjela Koblischka-Veneva
Jörg Schmauch
Masato Murakami
spellingShingle Michael R. Koblischka
Anjela Koblischka-Veneva
Jörg Schmauch
Masato Murakami
Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
Materials
iron-based superconductors
critical currents
flux pinning
microstructure
author_facet Michael R. Koblischka
Anjela Koblischka-Veneva
Jörg Schmauch
Masato Murakami
author_sort Michael R. Koblischka
title Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
title_short Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
title_full Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
title_fullStr Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
title_full_unstemmed Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> Powders
title_sort microstructure and flux pinning of reacted-and-pressed, polycrystalline ba<sub>0.6</sub>k<sub>0.4</sub>fe<sub>2</sub>as<sub>2</sub> powders
publisher MDPI AG
series Materials
issn 1996-1944
publishDate 2019-07-01
description The flux pinning properties of reacted-and-pressed Ba<sub>0.6</sub>K<sub>0.4</sub>Fe<sub>2</sub>As<sub>2</sub> powder were measured using magnetic hysteresis loops in the temperature range 20 K &#8804; <i>T</i> &#8804; 35 K. The scaling analysis of the flux pinning forces (<inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>F</mi> <mi>p</mi> </msub> <mo>=</mo> <msub> <mi>j</mi> <mi>c</mi> </msub> <mo>&#215;</mo> <mi>B</mi> </mrow> </semantics> </math> </inline-formula>, with <inline-formula> <math display="inline"> <semantics> <msub> <mi>j</mi> <mi>c</mi> </msub> </semantics> </math> </inline-formula> denoting the critical current density) following the Dew-Hughes model reveals a dominant flux pinning provided by normal-conducting point defects (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>&#948;</mi> <mi>l</mi> </mrow> </semantics> </math> </inline-formula>-pinning) with only small irreversibility fields, <inline-formula> <math display="inline"> <semantics> <msub> <mi>H</mi> <mi>irr</mi> </msub> </semantics> </math> </inline-formula>, ranging between 0.5 T (35 K) and 16 T (20 K). Kramer plots demonstrate a linear behavior above an applied field of 0.6 T. The samples were further characterized by electron backscatter diffraction (EBSD) analysis to elucidate the origin of the flux pinning. We compare our data with results of Weiss et al. (bulks) and Yao et al. (tapes), revealing that the dominant flux pinning in the samples for applications is provided mainly by grain boundary pinning, created by the densification procedures and the mechanical deformation applied.
topic iron-based superconductors
critical currents
flux pinning
microstructure
url https://www.mdpi.com/1996-1944/12/13/2173
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AT anjelakoblischkaveneva microstructureandfluxpinningofreactedandpressedpolycrystallinebasub06subksub04subfesub2subassub2subpowders
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