LAUSR

Abstract Novel low temperature sol-gel route for the synthesis nanostructured Hausmanite, Mn3O4with very small crystallite size (9±1 nm) and phase purity is reported. Reaction temperature of 0–5°C and drying temperature of 40°C is the lowest reported so far. Average particle size (8±1 nm) measured from Transmission Electron Microscopy is in good agreement with the crystallite size indicating monodispersed nature. Raman analysis indicates the presence of +4 valence states for Mn over and above +2 and +3and the presence of an Mn2O3 like surface layer. XPS analysis confirms the phase purity as well as the presence of Mn4+ions. Presence of +4 valence state for Mn is attributed to the presence of cation vacancies that lead to disproportionate reactions. UV-visible absorption spectra is quite broad with charge transitions associated with Mn2+, Mn3+ and Mn4+ statesand d-d crystal field transitions. DC electrical conductivity is about two orders of magnitude higher than that of single crystalline Mn3O4 and the conduction mechanism is defect dependent.