Benefit of high-pressure structure on sodium transport properties: Example with NaFeF3 post-perovskite
Kevin Lemoine,
Agnieszka Wizner,
Sandy Auguste,
Jean-Marc Grenèche,
Hiroshi Kojitani,
Masaki Akaogi,
Yoshiyuki Inaguma
Affiliations
Kevin Lemoine
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan; Corresponding author.
Agnieszka Wizner
Center for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, 01510, Vitoria-Gasteiz, Spain; University of the Basque Country (UPV/EHU), Barrio Sarriena, s/n, 48940, Leioa, Spain
Sandy Auguste
Institut des Molécules et des Matériaux du Mans, UMR CNRS 6283, Le Mans Université, Avenue Olivier Messiaen, 72085, Le Mans Cedex 9, France
Jean-Marc Grenèche
Institut des Molécules et des Matériaux du Mans, UMR CNRS 6283, Le Mans Université, Avenue Olivier Messiaen, 72085, Le Mans Cedex 9, France
Hiroshi Kojitani
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
Masaki Akaogi
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
Yoshiyuki Inaguma
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
In the search of promising Na-ion cathode materials, high-pressure synthesis method was applied to obtain sodium iron fluoride NaFeF3 with the post-perovskite lamellar structure. A two-step synthesis was performed: first, the Pnma orthorhombic perovskite structure NaFeF3 form (or Pv-NaFeF3, GdFeO3 type) was synthesized at 1270 K and 7.7 GPa, then the Cmcm orthorhombic post-perovskite structure (or pPv-NaFeF3, CaIrO3 type) was obtained using a second step at 700 K and 15 GPa. The post-perovskite form was stabilized under ambient conditions with a low amount of remaining perovskite phase (5 mol%). The Mössbauer analysis of pPv-NaFeF3 was firstly investigated with a paramagnetic structure obtained at 300 and 77 K, opposed to Pv-NaFeF3 magnetism reflecting the different [FeF6] polyhedra arrangements. Finally, the sodium migration within the framework of both structures was evaluated with the use of Bond Valence Energy Landscape (BVEL) calculations, resulting with an enhanced Na+ mobility within the pPv-NaFeF3 structure.
