Preparation ofα-MnO2with an Open Tunnel

Yuji Muraoka, Hiroshi Chiba, Toshiyuki Atou, Masae Kikuchi, Kenji Hiraga, Yasuhiko Syono, Shoko Sugiyama, Sadaaki Yamamoto, Jean Claude Grenier

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56 Citations (Scopus)


A single-phaseα-MnO2without any large stabilizing cations was successfully prepared by starting from hollandite-type (NH4)xMn8O16and quenching from 440°C during heating in flowing Ar. The unit-cell dimension was determined by XRD analysis to bea=10.308(2) Å andc=2.854(1) Å. In comparison with that of the starting material (a=9.896(1) Å andc= 2.859(1) Å), theadimension increased while thecdimension changed little. No presence of ammonium ions in the structure of this specimen was shown by IR spectroscopy, the Kjeldahl analysis, or temperature-programmed-desorption (TPD) measurement. The structural change from the hollandite phase to Mn2O3was observed at 540°C. TPD analysis indicates the presence of nitrogen other than ammonium ions in the hollandite material we prepared, and also suggests that this nitrogen might have a strong chemical interaction to the hollandite structure.

Original languageEnglish
Pages (from-to)136-142
Number of pages7
JournalJournal of Solid State Chemistry
Issue number1
Publication statusPublished - Apr 1 1999
Externally publishedYes


  • 440°C
  • ammonium ion
  • hollandite structure
  • quench
  • α-MnO

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry


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