Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li$$_{1–x}$$Fe$$_x$$(OH)Fe$$_{1–y}$$Se

Sun, Hualei, Woodruff, Daniel N., Cassidy, Simon J., Allcroft, Genevieve M., Sedlmaier, Stefan J., Thompson, Amber L., Bingham, Paul A., Forder, Susan D., Cartenet, Simon, Mary, Nicolas, and others. (2015) Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li$$_{1–x}$$Fe$$_x$$(OH)Fe$$_{1–y}$$Se. Inorganic Chemistry, 54 (4). pp. 1958-1964. ISSN 0020-1669. E-ISSN 1520-510X. (doi:10.1021/ic5028702)

Abstract

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li$$_{1–x}$$Fex(OH)Fe$$_{1–y}$$Se (x$$\sim$$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 Li$$_{1–x}$$Fe$$_x$$(OH) reservoir layer to fill vacancies in the selenide layer.

Item Type: Article 10.1021/ic5028702 Physics of Quantum Materials Q Science > QC Physics > QC176 Solid state physicsQ Science > QD Chemistry > QD478 Solid State Chemistry Faculties > Sciences > School of Physical Sciences > Functional Materials Group Silvia Ramos 28 Apr 2015 10:01 UTC 06 Feb 2020 13:40 UTC https://kar.kent.ac.uk/id/eprint/48079 (The current URI for this page, for reference purposes) https://orcid.org/0000-0003-2725-7706