Two Variants of the 1/2[110]p(203)p Crystallographic Shear Structures: The Phasoid Sr0.61Pb0.18(Fe0.75Mn0.25)O2.29

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• 作者：Christophe Lepoittevin ; Joke Hadermann ; Sylvie Malo ; Olivier Prez ; Gustaaf Van Tendeloo ; Maryvonne Hervieu
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：September 7, 2009
• 年：2009
• 卷：48
• 期：17
• 页码：8257-8262
• 全文大小：962K
• 年卷期：v.48,no.17(September 7, 2009)
• ISSN：1520-510X

文摘

For the composition (Sr_0.61Pb_0.18)(Fe_0.75Mn_0.25)O_2.29, a new modulated crystallographic shear structure, related to perovskite, has been synthesized and structurally characterized by transmission electron microscopy. The structure can be described using a monoclinic supercell with cell parameters a_m = 27.595(2) Å, b_m = 3.8786(2) Å, c_m = 13.3453(9) Å, and β_m = 100.126(5)°, refined from powder X-ray diffraction data. The incommensurate crystallographic shear phases require an alternative approach using the superspace formalism. This allows a unified description of the incommensurate phases from a monoclinically distorted perovskite unit cell and a modulation wave vector. The structure deduced from the high-resolution transmission electron microscopy and high-angle annular dark-field−scanning transmission electron microscopy images is that of a 1/2[110]_p(203)_p crystallographic shear structure. The structure follows the concept of a phasoid, with two coexisting variants with the same unit cell. The difference is situated at the translational interface, with the local formation of double (phase 2) or single (phase 1) tunnels, where the Pb cations are likely located.