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Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]

Abstract: A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4  106 S cm1 at room temperature to 5.5  105 S cm1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements

 Fuente: RSC Adv., 2020, 10, 11200

Editorial: Royal Society of Chemistry

 Año de publicación: 2020

Nº de páginas: 10

Tipo de publicación: Artículo de Revista

DOI: 10.1039/d0ra00245c

ISSN: 2046-2069

Proyecto español: MAT2017-89239- C2-(1,2)-P

Url de la publicación: https://doi.org/10.1039/D0RA00245C

Autores/as

PALMERINA GONZALEZ IZQUIERDO

FABELO, OSCAR

BEOBIDE, GARIKOITZ

CANO, ISRAEL

RUIZ DE LARRAMENDI, IDOIA

VALLCORBA, ORIOL

FERNÁNDEZ-DÍAZ, MARÍA TERESA