Darstellung und Reaktionen von Psilomelan (Romanéchit) Ba2Mn15O30∙4H2O
Psilomelane Ba2Mn15O30∙4H2O was synthesized under hydrothermal conditions from Ba-7Å-phyllomanganate(IV) in BaCl2 solution. The topotactic reaction transforms the initial layer lattice into needles with tunnels twice the size of hollandite type tunnels. These are filled with unexchangeable Ba2+ ion...
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| Main Authors: | , |
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| Format: | Article |
| Language: | deu |
| Published: |
Swiss Chemical Society
1983-11-01
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| Series: | CHIMIA |
| Online Access: | https://www.chimia.ch/chimia/article/view/9598 |
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| Summary: | Psilomelane Ba2Mn15O30∙4H2O was synthesized under hydrothermal conditions from Ba-7Å-phyllomanganate(IV) in BaCl2 solution. The topotactic reaction transforms the initial layer lattice into needles with tunnels twice the size of hollandite type tunnels. These are filled with unexchangeable Ba2+ ions and water molecules which cannot be reversibly removed. Intergrowth with hollandite type microdomains is frequent and can be directly observed in the electron microscope. Thermal treatment of synthetic psilomelane leads via increasing intergrowth to hollandite BaMn8O16. Refluxing in acid produces after a month γ-MnO2 (and, in the end, β-MnO2). Synthetic psilomelane has no exchange properties. The M2 position in the lattice is occupied by Mn3+ ions which explain the elongated coordination octahedron as Jahn-Teller effect.
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| ISSN: | 0009-4293 2673-2424 |