Oxygen-deficiency-induced 6H-polymorph of hexagonal perovskite Ba4YMn3O11.5−δ: synthesis, structure and properties

Xiaojun Kuang; Hong Zhu; Mathieu Allix; Craig A. Bridges; Matthew J. Rosseinsky; Yuexiang Li

doi:10.1039/C2JM15845K

Oxygen-deficiency-induced 6H-polymorph of hexagonal perovskite Ba₄YMn₃O_11.5−δ: synthesis, structure and properties†

Xiaojun Kuang,*^ab Hong Zhu,^c Mathieu Allix,^bd Craig A. Bridges,^b Matthew J. Rosseinsky^b and Yuexiang Li^c

* Corresponding authors

^a MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, KLGHEI of Environment and Energy Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, P. R. China
E-mail: kuangxj@mail.sysu.edu.cn

^b Department of Chemistry, The University of Liverpool, Liverpool, United Kingdom

^c Department of Chemistry, Nanchang University, Nanchang 330031, P. R. China

^d CNRS, UPR3079 CEMHTI, 45071 Orléans cedex2, France and Université d'Orléans, Faculté des Sciences, 1D Avenue de la Recherche Scientifique, Avenue du Parc Floral, Orléans Cedex 2, France

Abstract

The 12-layer hexagonal perovskite Ba₄YMn₃O_11.5 (R [3 with combining macron] m, referred to as 12R) was transformed to a 6-layer mixed valent Mn^3+/4+ hexagonal perovskite Ba₄YMn₃O_10.7 (P6₃/mmc, referred to as 6H) via a partial-reduction in a N₂ flow. This phase transformation between the 12R and 6H phases is redox-reversible. In contrast with the 12R-type Ba₄YMn₃O_11.5 structure containing c-BaO_2.75 and h-BaO₃ layers with a (cchh)₃ stacking, the 6H-type Ba₄YMn₃O_10.7 structure consists of the cubic (c) BaO_2.87 and hexagonal (h) BaO_2.33 layers with a (cch)₂ stacking, showing a preference of oxygen vacancy distribution in the hexagonal layers over the cubic layers. The h-BaO_2.33 layer in the 6H-type Ba₄YMn₃O_10.7 transforms two-thirds of face-sharing octahedral Mn₂O₉ dimers into edge-sharing pyramidal Mn₂O₈ units, sharing corners with Y octahedra/pyramids. Impedance measurements suggested that the 6H-type material is insulating with a bulk electrical resistivity of ∼10⁷ Ω cm at 303 K, significantly higher than that for the 12R-type Ba₄YMn₃O_11.5 by ∼4 orders of magnitude.

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Article information

DOI: https://doi.org/10.1039/C2JM15845K
Article type: Paper
Submitted: 14 Nov 2011
Accepted: 22 Feb 2012
First published: 16 Mar 2012

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J. Mater. Chem., 2012,22, 8103-8109

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Oxygen-deficiency-induced 6H-polymorph of hexagonal perovskite Ba₄YMn₃O_11.5−δ: synthesis, structure and properties

X. Kuang, H. Zhu, M. Allix, C. A. Bridges, M. J. Rosseinsky and Y. Li, J. Mater. Chem., 2012, 22, 8103 DOI: 10.1039/C2JM15845K

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