Thermal stability of MnO2 polymorphs

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15 Citations (Scopus)


This study reports thermal stability of α, β, γ, δ, and λ-type MnO2 polymorphs investigated using differential scanning calorimetry (DSC) and in-situ high-temperature X-ray diffraction measurement (HTXRD). These experiments revealed that the thermal stability of the polymorphs is in the following order: β ​> ​α ​> ​γ ​> ​δ ​≈ ​λ. The β-MnO2 phase (1 ​× ​1 tunnel, rutile structure), the most stable form between the MnO2 polymorphs, maintains the structure up to 500 ​°C until oxygen release causes phase transformation to Mn2O3. The α-MnO2 phase (2 ​× ​2 and 1 ​× ​1 tunnel structure) exhibits high thermal stability comparable to the β phase, despite its large vacant 2 ​× ​2 tunnel. The γ-MnO2 phase (mixed microdomain structure of 2 ​× ​1 tunnel and 1 ​× ​1 tunnel) shows a stepwise transformation into β-MnO2 from 400 ​°C after structure relaxation. The δ-MnO2 phase (layered structure) is easily destabilized by extracting interlayer K ions, resultingly, to lose the interlayer periodicity below 200 ​°C, while each layer itself is preserved up to ∼500 ​°C. The λ-MnO2 phase (defect spinel structure) is thermally unstable and transforms into β-MnO2 around 250 ​°C, and subsequently decomposes to Mn2O3 above the temperature. The thermal stability of MnO2 polymorphs is discussed in terms of the bonding environment of oxide ions.

Original languageEnglish
Article number122683
JournalJournal of Solid State Chemistry
Publication statusPublished - 2022 Jan


  • In-situ high temperature X-ray diffraction
  • Manganese dioxides
  • Phase transformation
  • Polymorphic crystal structure
  • Thermal stability

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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