Nano-domain structure of Li4Mn5O12 spinel
| Autor: | Diana Nihtianova, Radostina Stoyanova, Sv. Ivanova, Ekaterina Zhecheva |
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| Rok vydání: | 2011 |
| Předmět: |
Materials science
Annealing (metallurgy) Mechanical Engineering Spinel Mineralogy engineering.material law.invention Metal Crystallography Octahedron Mechanics of Materials law visual_art visual_art.visual_art_medium engineering General Materials Science High-resolution transmission electron microscopy Spectroscopy Electron paramagnetic resonance Monoclinic crystal system |
| Zdroj: | Journal of Materials Science. 46:7098-7105 |
| ISSN: | 1573-4803 0022-2461 |
| Popis: | XRD-pure Li4Mn5O12 spinels are obtained below 600 °C from oxalate and acetate precursors. The morphology consists of nanometric particles (about 25 nm) with a narrow particle size distribution. HRTEM and electron paramagnetic resonance (EPR) spectroscopy of Mn4+ are employed for local structure analysis. The HRTEM images recorded on nano-domains in Li4Mn5O12 reveal its complex structure. HRTEM shows one-dimensional structure images, which are compatible with the (111) plane of the cubic spinel structure and the (001) plane of monoclinic Li2MnO3. For Li4Mn5O12 compositions annealed between 400 and 800 °C, EPR spectroscopy shows the appearance of two types of Mn4+ ions having different metal environments: (i) Mn4+ ions surrounded by Li+ and Mn4+ and (ii) Mn4+ ions in Mn4+-rich environment. The composition of the Li+, Mn4+-shell around Mn4+ mimics the local environment of Mn4+ in monoclinic Li2MnO3, while the Mn4+-rich environment is related with that of the spinel phase. The structure of XRD-pure Li4Mn5O12 comprises nano-domains with a Li2MnO3-like and a Li4/3−xMn5/3+xO4 composition rather than a single spinel phase with Li in tetrahedral and Li1/3Mn5/3 in octahedral spinel sites. The annealing of Li4Mn5O12 at temperature higher than 600 °C leads to its decomposition into monoclinic Li2MnO3 and spinel Li4/3−xMn5/3+xO4. |
| Databáze: | OpenAIRE |
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