First mixed-metal fluoride pyrochlores obtained by topotactic oxidation of ammonium fluorides under F2 gas - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Crystal Growth & Design Année : 2021

First mixed-metal fluoride pyrochlores obtained by topotactic oxidation of ammonium fluorides under F2 gas

Kévin Lemoine
Romain Moury
Marc Leblanc
Veyis Gunes

Résumé

Metal fluorides with 3D open structures, pyrochlore (pyr) or hexagonal tungsten bronze (HTB), are promising materials as positive electrodes for rechargeable batteries or catalysts. Herein, we have developed a two-step synthesis procedure to obtain new anhydrous mixed-metal-cation fluorides crystallizing in the pyrochlore structure. The first step consists of preparing mixed-metal ammonium fluorides (NH4)M2+Fe3+F6 (M = Mn, Fe, Co Ni) using different synthesis strategies. For M = Mn, three allotropic varieties of (NH4)Mn2+Fe3+F6 are obtained; two phases adopt the expected pyrochlore network with either the cubic Fm3̅m or the orthorhombic Pnma space group, and the third phase exhibits a 3D network with narrow pseudotriangular cavities. 57Fe Mössbauer spectrometry indicates that the crystal structures are governed by the Fe3+/Mn2+ cationic order or disorder. The second step is a topotactic oxidation of pyr-(NH4)M2+Fe3+F6 under a molecular F2 flow. To better understand the reaction mechanism, the topotactic oxidation was followed by thermogravimetry, XRD, FTIR, and Mössbauer spectrometry. The successful synthesis of the first anhydrous pyr-M3+0.5Fe0.5F3 provides a new route to prepare anhydrous mixed-metal fluorides pyrochlore with empty cavities of the open framework.

Domaines

Matériaux
Fichier non déposé

Dates et versions

hal-03167049 , version 1 (11-03-2021)

Identifiants

Citer

Kévin Lemoine, Romain Moury, Etienne Durand, Elena Arroyo-de Dompablo, Emilio Morán, et al.. First mixed-metal fluoride pyrochlores obtained by topotactic oxidation of ammonium fluorides under F2 gas. Crystal Growth & Design, 2021, 21 (2), pp.935-945. ⟨10.1021/acs.cgd.0c01279⟩. ⟨hal-03167049⟩
50 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More