The Crystal Structure of Ramsdellite, an Orthorhombic Modification of MnO2.

Byström, Ann Marie; Lund, E. Wang; Lund, L. Koren; Hakala, Maire

doi:10.3891/acta.chem.scand.03-0163

Cited by 148 publications

(74 citation statements)

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“…[21] For the ramsdellite MnO 2 , the Mn IV O 6 octahedra are linked in double chains, each consisting of two adjacent single chains that share octahedral edges; the double chains, in turn, link corners with each other to form a framework with tunnels that have a rectangular-shaped cross-section with 1 2 octahedra on a side. [22] For these two concerned structures, pyrolusite has a tetragonal system with the space group P4 2 /mnm and ramsdellite has an orthorhombic system in the Pnam space group, neither of which can exhibit hexagonal symmetry based on their space groups. Therefore, a contradiction occurs between the current hexagonal symmetry in the sample and the classical De Wolff model based on pyrolusite-ramsdellite intergrowth.…”

Section: Resultsmentioning

confidence: 99%

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Wu¹,

Xie²,

Zhang³

et al. 2008

Chemistry A European J

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Although about 200,000 metric tons of gamma-MnO(2) are used annually worldwide for industrial applications, the gamma-MnO(2) structure is still known to possess a highly ambiguous crystal lattice. To better understand the gamma-MnO(2) atomic structure, hexagon-based nanoarchitectures were successfully synthesized and used to elucidate its internal structure for the present work. The structural analysis results, obtained from the hexagon-based nanoarchitectures, clearly show the coexistence of akhtenskite (epsilon-MnO(2)), pyrolusite (beta-MnO(2)), and ramsdellite in the so-called gamma-MnO(2) phase and verified the heterogeneous phase assembly of the gamma-MnO(2) state, which violates the well-known "De Wolff" model and derivative models, but partially accords with Heuer's results. Furthermore, heterogeneous gamma-MnO(2) assembly was found to be a metastable structure under hydrothermal conditions, and the individual components of the heterogeneous gamma-MnO(2) system have structural similarities and a high lattice matches with pyrolusite (beta-MnO(2)). The as-obtained gamma-MnO(2) nanoarchitectures are nontoxic and environmentally friendly, and the application of such nanoarchitectures as support matrices successfully mitigates the common problems for phase-change materials of inorganic salts, such as phase separation and supercooling-effects, thereby showing prospect in energy-saving applications in future "smart-house" systems.

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Section: Resultsmentioning

confidence: 99%

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Wu¹,

Xie²,

Zhang³

et al. 2008

Chemistry A European J

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“…Unfortunately, this was not the case and we instead fitted an X-ray diffraction pattern that was calculated with the Rietveld program based on the structure proposed by Bystr6m (1949) (Fig. 5).…”

Section: Reliability Testmentioning

confidence: 99%

Fits of the γ-MnO2 Structure Model to Disordered Manganese Dioxides

Schilling¹,

Dahn²

1998

J Appl Cryst

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This paper defines F-MnO2 as a manganese dioxide phase with a structure based on an intergrowth of ramsdellitic and pyrolusitic domains, a model initially proposed by de Wolff [Acta Cryst. (1959), 12, 341-345].This model consists of a stochastic stacking of four different types of layers, each of which is based on the same underlying two-dimensional periodic lattice. An analytic expression for the scattered intensity as a function of scattering vector is given; the subsequent powder averaging to obtain the intensity as a function of scattering angle has to be performed partly numerically. This formalism is then utilized to fit experimentally observed powder X-ray diffraction patterns of typical disordered manganese dioxides with the F-MnO2 model. The model fits the chemically prepared manganese dioxide investigated here fairly well; heating it increases the pyrolusitic character. However, the structure of electrolytically prepared manganese dioxides (EMD) is not well described by this model, implying that there are other types of disorders in EMDs.

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“…Faulting (1965) describes nsutite as hexagonal in form; Bricker (1965) describes nsutite as lathlike in appearance. According to Bystrom (1949) and Swanson and others (1974), ramsdellite and partridgeite both may be orthorhombic. In light of the above, the micrographs show the crystal forms to be expected (table 6 and fig.…”

Section: Identification Of Microcrystalline Precipitatesmentioning

confidence: 95%

Characterization of mineral precipitates by electron microscope photographs and electron diffraction patterns

Lind¹

1983

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The Crystal Structure of Ramsdellite, an Orthorhombic Modification of MnO2.

Cited by 148 publications

References 0 publications

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Fits of the γ-MnO2 Structure Model to Disordered Manganese Dioxides

Characterization of mineral precipitates by electron microscope photographs and electron diffraction patterns

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The Crystal Structure of Ramsdellite, an Orthorhombic Modification of MnO2.

Cited by 148 publications

References 0 publications

Environmentally Friendly γ‐MnO2 Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Environmentally Friendly γ‐MnO2 Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Fits of the γ-MnO2 Structure Model to Disordered Manganese Dioxides

Characterization of mineral precipitates by electron microscope photographs and electron diffraction patterns

Contact Info

Product

Resources

About

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications

Environmentally Friendly γ‐MnO₂ Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications