Stabilization of over-stoichiometric Mn<sup>4+</sup> in layered Na<sub>2/3</sub>MnO<sub>2</sub>
STOYANOVA, R.
Institute of General and Inorganic Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
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Institute of General and Inorganic Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
STOYANOVA, R.
Institute of General and Inorganic Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Institute of General and Inorganic Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
NIHTIANOVA, D.
Institute of General and Inorganic Chemistry
Central Laboratory of Mineralogy and Crystallography
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Institute of General and Inorganic Chemistry
Central Laboratory of Mineralogy and Crystallography
Langue
en
Article de revue
Ce document a été publié dans
Journal of Solid State Chemistry. 2010, vol. 183, n° 6, p. 1372-1379
Elsevier
Résumé en anglais
Sodium manganates with nominal composition Na<sub>2/3</sub>MnO<sub>2</sub> were prepared by solid state reaction between Na<sub>2</sub>CO<sub>3</sub> and MnCO<sub>3</sub> at 1000 °C. The composition and structure of ...Lire la suite >
Sodium manganates with nominal composition Na<sub>2/3</sub>MnO<sub>2</sub> were prepared by solid state reaction between Na<sub>2</sub>CO<sub>3</sub> and MnCO<sub>3</sub> at 1000 °C. The composition and structure of Na<i><sub>x</sub></i>MnO<sub>2</sub> were controlled by the rate of cooling from the temperature of preparation. This is a consequence of the capability of Na<sub>2/3</sub>MnO<sub>2</sub> to accommodate over<i>-</i>stoichiometric Mn<sup>4+</sup> ions up to 12.5%. Structural characterization was carried out by XRD powder diffractions, TEM analysis and Raman spectroscopy. The composition and oxidation state of manganese were determined by chemical analysis and magnetic susceptibility measurements. The manganese distribution in the layers was analysed using electron paramagnetic resonance (EPR) spectroscopy. By quenching from 1000 °C, the orthorhombic distorted modification is stabilized. A phase separation into orthorhombic and hexagonal modifications takes place when Na<sub>2/3</sub>MnO<sub>2</sub> is slow cooled. The structure changes are concomitant with an increase in the oxidation state of Mn. The over<i>-</i>stoichiometric Mn<sup>4+</sup> ions are accommodated in the hexagonal modification by creation of vacancies in the MnO<sub>2</sub><i>-</i>layers.< Réduire
Mots clés en anglais
Layered oxides
Sodium manganates
Electron paramagnetic resonance spectroscopy
Raman spectroscopy
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