Oxygen Vacancy Ordering in the Double-layered Ruddlesden−Popper Cobaltite Sm2BaCo2O7−δ

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• 作者：Lisa J. Gillie ; Joke Hadermann ; Maryvonne Hervieu ; Antoine Maignan ; Christine Martin
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：October 14, 2008
• 年：2008
• 卷：20
• 期：19
• 页码：6231-6237
• 全文大小：309K
• 年卷期：v.20,no.19(October 14, 2008)
• ISSN：1520-5002

文摘

A new oxygen-deficient Ruddlesden−Popper (RP) cobaltite Sm₂BaCo₂O_7−δ (δ ≈ 1.0) has been synthesized and the crystal structure elucidated by Rietveld analysis of X-ray powder diffraction (XRD) data and transmission electron microscopy (TEM). The phase crystallizes in a primitive orthorhombic unit cell, with lattice parameters a = 5.4371(4) Å; b = 5.4405(4) Å and c = 19.8629(6) Å, and space group Pnnm. Contrary to other oxygen-deficient cobalt RP phases, the oxygen vacancies are located in the equatorial positions of the [CoO] layers to give an intralayer structure similar to Sr₂Mn₂O₅, which is not usually observed for cobalt-containing materials. The Sm³⁺ and Ba²⁺ cations show a strong preference for distinct sites, with the majority of the larger Ba²⁺ cations situated in the perovskite block layers and Sm³⁺ cations predominantly in the rock salt layers. Magnetic susceptibility data demonstrate the strong antiferromagnetic (AFM) character of Sm₂BaCo₂O_7−δ.