Tunable Potassium Ion Conductivity and Magnetism in Substituted Layered Ferrates

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Contributors

Abstract

Five substituted oxohydroxoferrates K2–x(Fe,M)4O7–y(OH)y (M=Si, Ge, Ti, Mn, Ir) were synthesized in a potassium hydroxide hydroflux with a molar base-water ratio q(K) of about 0.9. While the hexagonal prisms of K2–x(Fe,Ti)4O7–y(OH)y crystallize in P63/mcm, all other compounds form hexagonal plates with the trigonal space group P (Formula presented.) 1 m. The crystal structure of the oxohydroxoferrates resembles ß-alumina. It consists of honeycomb layers (Formula presented.) Fe2O6] of edge-sharing [FeO6] octahedra, where the hexagonal voids are capped by vertex-sharing [FeO4] tetrahedra pairs. The cavities between the oxoferrate layers host the potassium ions. Depending on M, the substitution affects different iron positions and varies between 5 and 20 %. The magnetic structures of the antiferromagnetic compounds were determined by neutron powder diffraction. The potassium ion conductivity was characterized by electrochemical impedance spectroscopy at room temperature. By storing the oxohydroxoferrates in air or annealing them at 700 °C the ion conductivity was significantly increased, e. g. to 5.0 ⋅ 10−3 S cm−1 for a pressed pellet of the iridium substituted compound.

Details

Original languageEnglish
Pages (from-to)364-376
Number of pages13
JournalEuropean Journal of Inorganic Chemistry
Volume2021
Issue number4
Publication statusPublished - 2021
Peer-reviewedYes

External IDs

researchoutputwizard legacy.publication#87783
Scopus 85097410135
RIS urn:4C08F8552109FACF7C342349EE135F6E
ORCID /0000-0001-7523-9313/work/159171513
ORCID /0000-0002-2391-6025/work/159171889

Keywords

Keywords

  • crystal structure, ferrate, ion conductivity