Study by thermogravimetry, electrical conductivity and IR spectrometry of the phase transition for manganese cation deficient spinels

Abstract

Thermogravimetry, electrical conductivity and IR spectrometry were used to study the crystal structure change of the metastable manganese cation deficient spinels that occur during the oxidation of manganese ions above 500° C. The kinetic of the transformation is found to be governed by a nucleation growth mechanism with an activation energy varying with the amount of Mn3+ ions. The nature of the inversion products depends on the manganese substitution extent. We observe for a substitution extent x 0.72 a mixture of two phases α-(MnFe)2O3 + Mn2O3 of orthorhombic structure.