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Crystal structures of synthetic 7 Å and 10 Å manganates substituted by mono- and divalent cations

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Title: Crystal structures of synthetic 7 Å and 10 Å manganates substituted by mono- and divalent cations
Authors: Kuma, Kenshi Browse this author →KAKEN DB
Usui, Akira Browse this author
Paplawsky, William Browse this author
Gedulin, Benjamin Browse this author
Arrhenius, Gustaf Browse this author
Keywords: 7 Å manganate
10 Å manganate
X-ray diffraction
Electron diffraction
Crystal structure
Issue Date: Sep-1994
Publisher: Mineralogical Society
Journal Title: Mineralogical magazine
Volume: 58
Issue: 392
Start Page: 425
End Page: 447
Publisher DOI: 10.1180/minmag.1994.058.392.08
PMID: 11539554
Abstract: The crystal structures of synthetic 7 Å and 10 Å manganates, synthetic birnessite and buserite, substituted by mono- and divalent cations were investigated by X-ray and electron diffractions. The monoclinic unit cell parameters of the subcell of lithium 7 Å manganate, which is one of the best ordered manganates, were obtained by computing the X-ray powder diffraction data: a = 5.152 Å, b = 2.845 Å, c = 7.196 Å, β = 103.08°. On the basis of the indices obtained by computing the X-ray diffraction data of Li 7 Å manganate, monovalent Na, K and Cs and divalent Be, Sr and Ba 7 Å manganates were interpreted as the same monoclinic structure with β = 100–103° as that of Li 7 Å manganate, from their X-ray diffraction data. In addition, divalent Mg, Ca and Ni 10 Å manganates were also interpreted as the same monoclinic crystal system with β = 90–94° The unit cell parameters, especially a, c and β, change possibly with the type of substituent cation probably because of the different ionic radius, hydration energy and molar ratio of substituent cation to manganese. However, these diffraction data, except for those of Sr and Ba 7 Å and Ca and Ni 10 Å manganates, reveal only some parts of the host manganese structure with the edge-shared [MnO6] octahedral layer. On the other hand, one of the superlattice reflections observed in the electron diffractions was found in the X-ray diffraction lines for heavier divalent cations Sr and Ba 7 Å and Ca and Ni 10 Å manganates. The reflection presumably results from the substituent cation position in the interlayer which is associated with the vacancies in the edge-shared [MnO6] layer and indicates that the essential vacancies are linearly arranged parallel to the b-axis. Furthermore, the characteristic superlattice reflection patterns for several cations, Li, Mg, Ca, Sr, Ba and Ni, manganates were interpreted that the substituent cations are regularly distributed in the interlayer according to the exchange percentage of substituent cation to Na+. In contrast, the streaking in the a-direction observed strongly in the electron diffractions for heavier monovalent cations, K and Cs, manganates probably results from the disordering of their cations in the a-direction in the interlayer.
Type: article
URI: http://hdl.handle.net/2115/53250
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 久万 健志

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