Raman spectra of birnessite manganese dioxides

Structural features of layered manganese dioxides of the bimessite family are studied using Raman scattering spectroscopy. This local probe is capable of analysing directly the near-neighbour environment of oxygen coordination around manganese and lithium cations. Four types of sol-gel bimessite (SGB) are considered: lithium bimessite (Li-Bir), sodium bimessite (Na-Bir), sol-gel bimessite (SG-Bir), and sol-gel Co-doped bimessite (SGCo-Bir). Thus, in a first approach, we consider the overall spectral features of birnessites such as the superposition of the spectra of local structures, while the lattice modes are discussed in the spectroscopic symmetry. Results show the specific spectroscopic fingerprints of SG-Bir single phases, the site occupancy of Co ions in the substituted SGCo-Bir compound, and vibrations due to lithium ions with their oxygen neighbours in Li-Bir, Li(0.32)MnO(2)(.)0.6H(2)O. A correlation between the interlayer d-spacing and the stretching mode frequencies of bimessite oxides has been established. (C) 2003 Elsevier Science B.V. All rights reserved.