High Dilution of Anionic Vacancies in Sr0.8Ba0.2Fe(O,F)2.5
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- 作者：Mihai Sturza ; Sylvie Daviero-Minaud ; Marielle Huv茅 ; Nicolas Renaut ; Nicolas Tiercelin ; Olivier Mentr茅
- 刊名：Inorganic Chemistry
- 出版年：2011
- 出版时间：December 19, 2011
- 年：2011
- 卷：50
- 期：24
- 页码：12499-12507
- 全文大小：555K
- 年卷期：v.50,no.24(December 19, 2011)
- ISSN：1520-510X
文摘
The (Ba,Sr)FeO3鈭捨?/sub> system is known for its strong tendency for oxygen and vacancies to order into several forms including fully ordered pseudobrownmillerites, hexagonal perovskites with segregation of the vacancies in particular anionic layers and low deficient (pseudo)cubic compounds (generally 未 < 0.27, Fe3/4+). We show for the first time, using a simple chemical process, the easy access to a large amount of vacancies (未 鈮?0.5, Fe3+) within the room-temperature stable tetragonal (pseudocubic) Sr0.8Ba0.2FeF0.1(O,F)2.5. The drastic effect of the incorporation of a minor amount of fluoride passes through the repartition of local O/F/鈻?constraints shifting the tolerance factor into the pseudocubic range for highly deficient compounds. It is stable up to 670 K, where an irreversible reoxidation process occurs, leading to the cubic-form. The comparison with the cubic oxide Sr0.8Ba0.2FeO2.7 shows the increase of the resistivity (3D-VRH model) by two decades due to the almost single valent Fe3+ of the oxofluoride. In addition, the G-type magnetic ordering shows relatively weak moment for Fe3+ cations (MFe 鈮?2.64(1) 渭B at room temperature) attributed to incoherent magnetic components expected from local disorder in such anionic-deficient compounds.