A CLOSE LOOK AT ELECTROLYTIC MANGANESE DIOXIDE (EMD) AND THE γ-MnO2 & ε-MnO2 PHASES USING RIETVELD MODELING

Electrolytic Manganese Dioxide (EMD) material was analyzed by Rietveld refinement of x-ray diffraction patterns to answer the question, “Is EMD composed of gamma- or epsilon-MnO2?” An electron diffraction study of EMD using a 20 nanometer spot size electron beam reported observing only the e-MnO2 structure and no γ-MnO2 structure. However, a Transmission Electron Microscopy (TEM) study of EMD observed only γMnO2 structure as revealed by atom planes with a 0.4 nanometer spacing along with crystal twinning. Rietveld refinement results of EMD x-ray diffraction patterns indicate that EMD can be adequately described using both the gamma- and epsilon-manganese dioxide (γ-MnO2 and e-MnO2) phases with an occasional occurrence of pyrolusite (βMnO2). It is proposed that the e-MnO2 structure observed in both electron and x-ray diffraction patterns is only a signature of a disordered manganese occupancy of the long range hexagonal oxygen framework and not a discrete phase, and EMD material predominately composed of short range ordered γ-MnO2.