Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals

dc.contributor.author Liu, Yong
dc.contributor.author Xing, Qingfeng
dc.contributor.author Dennis, Kevin
dc.contributor.author McCallum, R.
dc.contributor.author Lograsso, Thomas
dc.contributor.department Ames National Laboratory
dc.contributor.department Materials Science and Engineering
dc.date 2018-05-29T17:08:36.000
dc.date.accessioned 2020-06-29T23:27:15Z
dc.date.available 2020-06-29T23:27:15Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2012
dc.date.embargo 2013-09-20
dc.date.issued 2012-10-01
dc.description.abstract <p>We study the relationship between precipitate morphology and superconductivity in K<sub>x</sub>Fe<sub>1.6+y</sub>Se<sub>2</sub> single crystals grown by self-flux method. Scanning electron microscopy (SEM) measurements revealed that the superconducting phase forms a network in the samples quenched above iron vacancy order-disorder transition temperature T<sub>s</sub>, whereas it aggregates into micrometer-sized rectangular bars and aligns as disconnected chains in the furnace-cooled samples. Accompanying this change in morphology the superconducting shielding fraction is strongly reduced. By post-annealing above T<sub>s</sub> followed by quenching in room temperature water, the network recovers with a superconducting shielding fraction approaching 80% for the furnace-cooled samples. A reversible change from network to bar chains was realized by a secondary heat treatment in annealed samples showing a large shielding fraction, that is, heating above T<sub>s</sub> followed by slow cooling across T<sub>s</sub>. The large shielding fraction observed in K<sub>x</sub>Fe<sub>1.6+y</sub>Se<sub>2</sub> single crystals actually results from an uniform and contiguous distribution of superconducting phase. Through the measurements of temperature dependent x-ray diffraction, it is found that the superconducting phase precipitates while the iron vacancy ordered phase forms together by cooling across T<sub>s</sub> in K<sub>x</sub>Fe<sub>1.6+y</sub>Se<sub>2</sub> single crystals. It is a solid solution above T<sub>s</sub>, where iron atoms randomly occupy both Fe1 and Fe2 sites in the iron vacancy disordering status; and phase separation is driven by the iron vacancy order-disorder transition upon cooling. However, neither additional iron in the starting mixtures nor as-quenching at high temperatures can extend the miscibility gap to the KFe<sub>2</sub>Se<sub>2</sub> side.</p>
dc.description.comments <p>This article is published as Liu, Yong, Qingfeng Xing, Kevin W. Dennis, R. William McCallum, and Thomas A. Lograsso. "Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in K x Fe 1.6+ y Se 2 single crystals." <em>Physical Review B</em> 86, no. 14 (2012): 144507. DOI: <a href="http://dx.doi.org/10.1103/PhysRevB.86.144507" target="_blank">10.1103/PhysRevB.86.144507</a>. Posted with permission.<em><br /></em></p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/ameslab_pubs/38/
dc.identifier.articleid 1036
dc.identifier.contextkey 4609103
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath ameslab_pubs/38
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/7945
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/ameslab_pubs/38/0-2015_Lograsso_ErratumEvolutionPrecipitate.pdf|||Fri Jan 14 23:51:39 UTC 2022
dc.source.bitstream archive/lib.dr.iastate.edu/ameslab_pubs/38/2012_LiuY_EvolutionPrecipitateMorphology.pdf|||Fri Jan 14 23:51:41 UTC 2022
dc.source.uri 10.1103/PhysRevB.86.144507
dc.subject.disciplines Condensed Matter Physics
dc.subject.disciplines Materials Science and Engineering
dc.supplemental.bitstream 2015_Lograsso_ErratumEvolutionPrecipitate.pdf
dc.title Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals
dc.type article
dc.type.genre article
dspace.entity.type Publication
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