Electronic behavior of three oxygen non-stoichiometric Fe4+/Fe3+ oxoperovskites

✍ Scribed by H.D. Zhou; J.B. Goodenough

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 320 KB
• Volume: 178
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2005.09.020

✦ Synopsis

For comparison with the Mn 4+ /Mn 3+ oxoperovskites at the crossover from localized to itinerant behavior of the s-bonding e electrons, the electronic properties of three oxygen non-stoichiometric, mixed-valent Fe 4+ /Fe 3+ oxoperovskites were explored by measuring their resistivity r(T), thermoelectric power a(T), and magnetic susceptibility w(T). Oxidation of Ca 2 Fe 2 O 5 by annealing in ozone progresses by oxygen insertion to give conductive CaFeO 3 perovskite clusters in a localized-electron, weakly oxidized brownmillerite Ca 2 Fe 2 O 5+d matrix. Removal of 0.12 oxygen per formula unit from La 1/3 Sr 2/3 FeO 3 lowers somewhat its cooperative disproportionation reaction, and fivefold-coordinated ions neighboring oxygen vacancies in the more ionically bonded slabs act as donors to the covalently bonded Fe(V)O 6 planes. Single-crystal SrFeO 2.83 exhibited bad-metal behavior with superparamagnetic, electron-rich fluctuations below 240 K that, on cooling below 190 K, become progressively trapped by the oxide-ion vacancies as an immobile second phase; long-range antiferromagnetic order is stabilized below a T N E60 K.