Synthesis of Superconducting Nanocables of FeSe Encapsulated in Carbonaceous Shell


The recent discovery of superconductivity in iron selenide has attracted considerable attention due to the simplicity of composition, unconventional nature of superconductivity, and ease of synthesis. We have synthesized superconducting FeSe nanowires with a simple catalyst-aided vapor transport reaction at 800 C in an inert atmosphere. The precursors were chosen to be elemental Se and iron acetylacetonate [FeIII(C5H 8O2)3]. These vaporized very easily, thereby facilitating transport, and also contributed to the formation of a carbonaceous shell encapsulating the FeSe nanowires. The superconductivity of these nanocables was confirmed through magnetic measurements and a Tc of ≈8 K was obtained for an ensemble of nanocables. The length of FeSe filling inside the carbon nanofibers could be varied by controlling the reaction conditions while the diameter of nanowires was dependent on the thickness of Au-Pd coating used as a catalyst. Extensive analysis through high-resolution microscopy revealed that there was considerable lattice contraction of FeSe in the nanocable up to about 3.6% along the c-direction leading to a reduced spacing between the (001) lattice planes. Interestingly, this compression was more pronounced near the catalyst-FeSe interface and was reduced further along the length of the nanocable. The presence of carbon nanofibers as a shell around the FeSe protected the FeSe nanowires from both atmospheric O2 and moisture attack, as was evident from the very long ambient condition shelf life of these nanocables, and also makes them more stable under e-beam irradiation.



Keywords and Phrases

Ambient Conditions; Carbonaceous Shell; Core-Shell Nanowires; E-Beam Irradiation; High-Resolution Microscopy; Inert Atmospheres; Iron Acetylacetonate; Iron Selenide; Lattice Contraction; Lattice Plane; Moisture Attack; Nanocables; Pnictides; Reaction Conditions; Shelf Life; Superconducting Nanowire; Vapor-Transport Reaction; Carbon Nanofibers; Catalysts; Nanowires; Shells (structures); Synthesis (chemical); Vapors; Superconductivity

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