Electrochemical Synthesis and Crystal Structure of the Organic Ion Intercalated Superconductor (TMA)0.5Fe2Se2 with Tc = 43 K

Bettina Rendenbach; Timotheus Hohl; Sascha Harm; Constantin Hoch; Dirk Johrendt

doi:10.1021/jacs.0c13396

Electrochemical Synthesis and Crystal Structure of the Organic Ion Intercalated Superconductor (TMA)_0.5Fe₂Se₂ with T_c = 43 K

J Am Chem Soc. 2021 Mar 3;143(8):3043-3048. doi: 10.1021/jacs.0c13396. Epub 2021 Feb 17.

Authors

Bettina Rendenbach¹, Timotheus Hohl¹, Sascha Harm¹, Constantin Hoch¹, Dirk Johrendt¹

Affiliation

¹ Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (D), 81377 München, Germany.

PMID: 33595300
DOI: 10.1021/jacs.0c13396

Abstract

Intercalation of organic cations in superconducting iron selenide can significantly increase the critical temperature (T_c). We present an electrochemical method using β-FeSe crystals (T_c ≈ 8 K) floating on a mercury cathode to intercalate tetramethylammonium ions (TMA⁺) quantitatively to obtain bulk samples of (TMA)_0.5Fe₂Se₂ with T_c = 43 K. The layered crystal structure is closely related to the ThCr₂Si₂-type with disordered TMA⁺ ions between the FeSe layers. Although the organic ions are not detectable by X-ray diffraction, packing requirements as well as first-principle density functional theory calculations constrain the specified structure. Our synthetic route enables electrochemical intercalations of other organic cations with high yields to greatly optimize the superconducting properties and to expand this class of high-T_c materials.