Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li

DOI: 10.1021/ic5028702

Authors: Hualei Sun (University of Oxford) , Daniel Woodruff (University of Oxford) , Simon Cassidy (University of Oxford) , Genevieve M. Allcroft (University of Oxford) , Stefan Sedlmaier (University of Oxford) , Amber Thompson (University of Oxford) , Paul Bingham (Sheffield Hallam University) , Susan D. Forder (Sheffield Hallam University) , Simon Cartenet (Sheffield Hallam University) , Nicolas Mary (Sheffield Hallam University) , Silvia Ramos (University of Kent) , Francesca Foronda (University of Oxford) , Benjamin H. Williams (University of Oxford) , Xiaodong Li (Beijing Synchrotron Radiation Facility) , Stephen J. Blundell (University of Oxford) , Simon J Clarke (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry , VOL 54 (4)

State: Published (Approved)
Published: January 2015
Diamond Proposal Number(s): 9697 , 9981 , 11061

Abstract: Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li1–xFex(OH)Fe1–ySe (x approx. 0.2; 0.02 < y < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low (y < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li1–xFex(OH) reservoir layer to fill vacancies in the selenide layer.

Subject Areas: Chemistry, Materials, Physics


Instruments: B18-Core EXAFS , I11-High Resolution Powder Diffraction , I19-Small Molecule Single Crystal Diffraction

Other Facilities: ISIS - Neutron Diffraction

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