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Relation between Composition and Crystalline Structure in Substituted CaKFe4as4

TitoloRelation between Composition and Crystalline Structure in Substituted CaKFe4as4
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2023
AutoriDuchenko, Anastasiya, Masi Andrea, Augieri Andrea, Barba Luisa, Campi Gaetano, Celentano Giuseppe, Gigli Lara, Plaisier Jasper, Pompeo Nicola, Rizzo Francesco, and Varsano F.
RivistaIEEE Transactions on Applied Superconductivity
Type of ArticleArticle
Parole chiave1144 superconductor, Alkaline earth, Alkalines, alkalinity, Barium compounds, Composition structure, Compound, Crystalline materials, Crystalline structure, CTE, Doping (additives), Iron Compounds, Iron-based Superconductors, Sodium, Substituted compounds, Superconducting transition temperature, Thermal expansion, X ray diffraction analysis, X- ray diffractions

1144 is a family of Iron Based Superconducting compound that attracts interest due to its regular structure, composed by an alternance of alkaline and alkaline-earth planes that intercalate Fe-As layers. This rigidity grants to 1144 compounds a stoichiometric nature, and thus a robust critical temperature not affected by chemical inhomogeneities, and a peculiar pinning landscape enhancing critical currents at high fields. Critical currents can be however further enhanced by introducing further defects by means of irradiation and chemical doping on the Fe site. In our works, as a different approach, we evaluate the effect of the alkaline and alkaline-earth aliovalent substitutions. For this scope, CaKFe4As4 polycrystalline powders have been successfully doped by partially replacing Ca with Na and K with Ba by means of a mechanochemically assisted thermal synthesis. Such substituted compounds crystallize in the P4/mmm structure typical of 1144 compounds. X-ray diffraction analysis revealed that depending on the level of substitution the reflections characteristic of the P4/mmm tend to vanish. In particular, peaks analysis has shown that doping introduces increasing disorder in selected crystalline planes. Barium and sodium, as dopant, do not act the same way, the latter being less invasive, so that 1144 structure is preserved up to 40% substitution. The contemporary replacement of potassium and calcium with barium and sodium exhibits an intermediate behavior. Analysis of X-ray diffraction profiles collected as a function of temperature down to 100K allowed to calculate the thermal expansion coefficients for the synthesized compounds, with CTE values similar for pristine and substituted compounds close to 1×10-6K-1 and 3×10-5K-1 respectively along the a-axis and c-axis. IEEE


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Citation KeyDuchenko20231