A New Manganite with an Original Composite Tunnel Structure: Ba6Mn24O48

ISSN： 0022-4596

Source： Journal of Solid State Chemistry, Vol.132, Iss.2, 1997-09, pp. : 239-248

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Abstract

A new manganite Ba6Mn24O48 with an original tunnel structure has been synthesized. Its electron diffraction study shows that this new phase exhibits a composite structure, built up of two tetragonal I sublattices with a=18.2 A, c1=2.8 A, and c2=4.6 A. The high-resolution electron microscopy investigation shows that the octahedral [Mn4O8][infinity] host lattice consists of hollandite- and rutile-type columns sharing the edges of their MnO6 octahedra so that a new kind of ten-sided tunnel is generated. The powder X-ray diffraction study confirms that the first sublattice (a, c1) corresponds to the [Mn4O8][infinity] framework. The second sublattice (a, c2) is associated with the barium network. The incommensurate modulated superstructural spots in the "a, c2" sublattice are correlated to both the occupancy and displacive modulation of the barium ions in the two kinds of tunnels.