Abstract
Sodium manganates with nominal composition Na 2/3MnO 2 were prepared by solid state reaction between Na 2CO 3 and MnCO 3 at 1000 °C. The composition and structure of Na x MnO 2 were controlled by the rate of cooling from the temperature of preparation. This is a consequence of the capability of Na 2/3MnO 2 to accommodate over ‐stoichiometric Mn 4+ 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 2/3MnO 2 is slow cooled. The structure changes are concomitant with an increase in the oxidation state of Mn. The over ‐stoichiometric Mn 4+ ions are accommodated in the hexagonal modification by creation of vacancies in the MnO 2 ‐layers.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
