OXIDATION MECHANISM AND VALENCE STATES OF COPPER AND MANGANESE IN TETRAGONAL CUMN2O4

With the view of determining the ionic configuration in tetragonal CuM n2O4 spinels prepared between 850 and 930 degrees C, the valence state s of copper and manganese and the oxidation mechanism of these compoun ds have been determined by XPS, FTIR spectroscopy analyses and DTG mea surements. For unoxidized samples, XPS spectroscopy analysis shows a p redominately monovalent copper located in tetrahedral sites. Divalent copper in octahedral sites is also present, but at a lower level. Simi lar results are obtained for oxidized samples. FTIR data, upon oxidati on of Cu and Mn ions below 500 degrees C, confirm the formation of a m etastable spinel phase Cu1.5Mn1.5O4 with a 1:3 ordering on the octahed ral sublattice. A quantitative analysis by DTG mainly based on the dif ference of reactivity of Cu and Mn ions allows measurement of the cont ent of each cation and determination of the ionic configuration.