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Tunable Potassium Ion Conductivity and Magnetism in Substituted Layered Ferrates
Author(s) -
Albrecht Ralf,
Hunger Jens,
Hoelzel Markus,
Suard Emmanuelle,
Schnelle Walter,
Doert Thomas,
Ruck Michael
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202000891
Subject(s) - chemistry , crystallography , conductivity , octahedron , potassium , antiferromagnetism , ion , magnetism , crystal structure , potassium hydroxide , inorganic chemistry , neutron diffraction , physics , organic chemistry , quantum mechanics , condensed matter physics
Five substituted oxohydroxoferrates K 2–x (Fe, M ) 4 O 7–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 K 2–x (Fe,Ti) 4 O 7–y (OH) y crystallize in P 6 3 / mcm , all other compounds form hexagonal plates with the trigonal space group P 3 ‾ 1 m . The crystal structure of the oxohydroxoferrates resembles ß ‐alumina. It consists of honeycomb layers∞ 2 Fe 2 O 6 ] of edge‐sharing [FeO 6 ] octahedra, where the hexagonal voids are capped by vertex‐sharing [FeO 4 ] 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.