RELATIONSHIPS BETWEEN COMPOSITION AND SURFACE-PROPERTIES OF THE DEHYDRATION PRODUCTS OF SYNTHETIC MANGANITE

The textural properties of manganese oxides are of great interest as they may limit the possible applicability of these compounds in redox catalysis or in the constitution of electrodes. The textural characteristics of the decomposition products of gamma -MnOOH in vacuo have been studied by the analysis of N//2 adsorption isotherms and by electron microscopy. Composition analysis using X-ray diffraction revealed that three consecutive processes take place with increasing temperature: manganite dehydration to gamma -Mn//2O//3, disproportionation to alpha -Mn//3O//4 and Mn//5O//8 and decomposition of the latter oxide to alpha -Mn//3O//4.