Evolution of oxygen-vacancy ordered crystal structures in the perovskite series SrnFenO3n-1 (n=2, 4, 8, and ∞), and the relationship to electronic and magnetic properties
Evolution of oxygen-vacancy ordered crystal structures in the perovskite series SrnFenO3n-1 (n=2, 4, 8, and ∞), and the relationship to electronic and magnetic properties
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DOI：
10.1006/jssc.1999.8640
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发表时间：
2000-05-01
影响因子：
3.3
通讯作者：
Kimball, CW
中科院分区：
文献类型：
--
作者：
Hodges, JP;Short, S;Kimball, CW
在2.5小于或等于x小于或等于3.0的氧组成范围内，SrFeOx系统以四种不同的化合物存在，其标称组成为SrnFenO 3 n-1（n = 2、4、8和无穷大）。端元SrFeO 3（n =无穷大）具有简单的立方钙钛矿晶体结构，而缺氧（n = 2、4和8）元各自采用不同的空位有序钙钛矿晶体结构。使用飞行时间中子粉末衍射，我们表明，以前提出的结构为Sr 4Fe 4 O 11（n = 4）和Sr 8 Fe 8 O23（n = 8）的化合物是不正确的。我们确定了Sr_4Fe_4O_（11）的正确晶体结构（斜方晶系，空间群Cmmm，a = 10.974（1）埃，B = 7.702（1）埃，c = 5.473（1）埃）和Sr 8 Fe 8 O23（四氢呋喃，空间群I4/mmm，a = 10.929（1）埃和c = 7.698（1）埃），通过比较候选模型和债券的Rietveld精化的拟合优度，每个模型的长度分布。使用正确的晶体结构，我们能够分配价态的Fe晶体学网站，并实现与发表的穆斯堡尔结果相同的化合物的一致性。(C)北京大学出版社.
Over the oxygen composition range 2.5 less than or equal to x less than or equal to 3.0, the SrFeOx system exists as four distinct compounds with the nominal composition SrnFenO3n-1 (n = 2, 4, 8, and infinity). The end member SrFeO3 (n = infinity) possesses a simple cubic perovskite crystal structure, whereas the oxygen-deficient (n = 2, 4, and 8) members each adopt a different vacancy-ordered perovskite crystal structure. Using time-of-flight neutron powder diffraction, we show that previously proposed structures for the Sr4Fe4O11 (n = 4) and Sr8Fe8O23 (n = 8) compounds are incorrect. We determine the correct crystal structures for Sr4Fe4O11 (orthorhombic, space group Cmmm, a = 10.974(1) Angstrom, b = 7.702(1) Angstrom, and c = 5.473(1) Angstrom) and Sr8Fe8O23 (tetragonal, space group I4/mmm, a = 10.929(1) Angstrom and c = 7.698(1) Angstrom) through comparisons of the goodness of fit for Rietveld refinements of candidate models and bond-length distributions for each model. Using the correct crystal structures, we are able to assign valence states to the Fe crystallographic sites and to achieve consistency with published Mossbauer results for the same compounds. (C) 2000 Academic Press.