Kinetic Study of the Solid State Reaction between Alpha-Fe2O3and ZnO for Zinc Ferrite Formation

Abstract

AbstractThe solid state reaction between ferric oxide and zinc oxide to form zinc ferrite was studied considering the variables of temperature, time and molar ratio of the reactant oxides. The reaction mixtures were analysed by X-ray diffraction and the external standard method was applied to follow the reaction quantitatively. The intensity of the strongest reflections of alpha-Fe2O3 and ZnO were measured and calibration graphs, prepared for standard mixtures, were used to calculate the fraction reacted, α. Selection of the strongest oxide lines improved the sensitivity and lowered the detection limit of the quantitative analysis. The nucleation of zinc ferrite was retarded in reaction mixtures with an excess of ferric oxide. The presence of zinc oxide, in ratios higher than equimolar, accelerated the reaction. Reaction data were analysed using kinetic equations corresponding to models of (a) diffusion, (b) nucleation and (c) phase boundary reaction. After an initial period at low temperature, during whi...