کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1334019 | 979131 | 2005 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Electronic behavior of three oxygen non-stoichiometric Fe4+/Fe3+ oxoperovskites Electronic behavior of three oxygen non-stoichiometric Fe4+/Fe3+ oxoperovskites](/preview/png/1334019.png)
For comparison with the Mn4+/Mn3+ oxoperovskites at the crossover from localized to itinerant behavior of the σ-bonding e electrons, the electronic properties of three oxygen non-stoichiometric, mixed-valent Fe4+/Fe3+ oxoperovskites were explored by measuring their resistivity ρ(T), thermoelectric power α(T), and magnetic susceptibility χ(T). Oxidation of Ca2Fe2O5 by annealing in ozone progresses by oxygen insertion to give conductive CaFeO3 perovskite clusters in a localized-electron, weakly oxidized brownmillerite Ca2Fe2O5+δ matrix. Removal of 0.12 oxygen per formula unit from La1/3Sr2/3FeO3 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)O6 planes. Single-crystal SrFeO2.83 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 TN≈60 K.
Temperature dependences of (a) resistivity ρ(T) and d(ln ρ)/d(1/T); (b) molar magnetic susceptibility χ(T) and its inverse 1/χ(T); and (c) thermoelectric power α(T) for Ca2Fe2O5.16. Inset of (c): Temperature dependences of magnetic susceptibility χ(T) and thermoelectric power α(T) for Ca2Fe2O5.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 178, Issue 12, December 2005, Pages 3679–3685