期刊
JOURNAL OF SOLID STATE CHEMISTRY
卷 181, 期 10, 页码 2601-2609出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2008.04.047
关键词
Ordered perovskites; Bismuth alkaline earth ferrites; Magneto-transport properties; Mossbauer study
资金
- European Union
Two-ordered perovskites, Bi1/3Sr2/3FeO2.67 and Bi1/2Ca1/2FeO2.75, have been stabilized and characterized by transmission electron microscopy, Mossbauer spectroscopy and X-ray powder diffraction techniques. They both exhibit orthorhombic superstructure, one with a approximate to b approximate to 2a(p) and c approximate to 3a(p) (S.G.: Pb2n or Pbmn) for the Sr-based compound and one with a approximate to b approximate to 2a(p) and c approximate to 8a(p) (S.G.:B222, Bmm2, B2mm or Bmmm) for the Ca-based one. The high-resolution transmission electron microscopy (HRTEM) images evidence the existence of one deficient [FeOx](y) layer, suggesting that Bi1/3Sr2/3FeO2.67 and Bi1/2Ca1/2FeO2.75 behave differently compared to their Ln-based homolog. The HAADF-STEM images allow to propose a model of cation ordering on the A sites of the perovskite. The Mossbauer analyses confirm the trivalent state of iron and its complex environment with three types of coordination. Both compounds exhibit a high value of resistivity and the inverse molar susceptibility versus temperature curves evidence a magnetic transition at about 730 K for the Bi1/3Sr2/3FeO2.67 and a smooth reversible transition between 590 and 650 K for Bi1/2Ca1/2FeO2.75. (c) 2008 Elsevier Inc. All rights reserved.
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