Layered perovskite-like Pb2Fe2O5 structure as a parent matrix for the nucleation and growth of crystallographic shear planes

Dmitry Batuk, Joke Hadermann, Artem Abakumov, Thomas Vranken, An Hardy, Marlies Van Bael, Gustaaf Van Tendeloo

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

The Pb2Fe2O5 compound with a layered intergrowth structure has been prepared by a solid-state reaction at 700 °C. The incommensurate compound crystallizes in a tetragonal system with a = 3.9037(2) Å, c = 3.9996(4) Å, and q = 0.1186(4)c*, or when treated as a commensurate approximant, a = 3.9047(2) Å, c = 36.000(3) Å, space group I4/ mmm. The crystal structure of Pb2Fe 2O5 was resolved from transmission electron microscopy data. Atomic coordinates and occupancies of the cation positions were estimated from high-angle annular dark-field scanning transmission electron microscopy data. Direct visualization of the positions of the oxygen atoms was possible using annular bright-field scanning transmission electron microscopy. The structure can be represented as an intergrowth of perovskite blocks and partially disordered blocks with a structure similar to that of the Bi 2O2 blocks in Aurivillius-type phases. The A-cation positions at the border of the perovskite block and the cation positions in the Aurivillius-type blocks are jointly occupied by Pb2+ and Fe 3+ cations, resulting in a layer sequence along the c axis: -PbO-FeO2- PbO-FeO2-Pb7/8Fe1/8- O1-x-Fe5/8Pb3/8-O2-Fe 5/8Pb3/8-. Upon heating, the layered Pb2Fe 2O5 structure transforms into an anion-deficient perovskite modulated by periodically spaced crystallographic shear (CS) planes. Considering the layered Pb2Fe2O5 structure as a parent matrix for the nucleation and growth of CS planes allows an explanation of the specific microstructure observed for the CS structures in the Pb-Fe-O system.

Original languageEnglish
Pages (from-to)4978-4986
Number of pages9
JournalInorganic Chemistry
Volume50
Issue number11
DOIs
Publication statusPublished - 6 Jun 2011
Externally publishedYes

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