An analysis of the grain growth kinetics in Mn₂O₃ nanocrystals

Abstract

The isothermal grain growth of Mn₂O₃ nanocrystals, prepared by the chemical liquid-phase homogeneous precipitation route, was investigated at various temperatures between 200 and 500 °C for different annealing times. X-ray diffraction patterns and transmission electron micrographs show that the average grain sizes are in the range of 4–50 nm. The grain growth data were analyzed using two different models. The first model, assuming normal grain growth as that in conventional polycrystalline materials, yields large grain growth exponent (n) and extremely low activation energy (Q). Although it can describe the evolution of grain sizes, it fails to give satisfactory physical interpretation of n and Q, both beyond the theoretical predictions. The second model is based on the structural relaxation of the interface component in nanocrystalline materials. In this case, the ordering of distorted interfaces by structural relaxation proceeds with grain growth. This structure relaxation model not only describes the evolutions of grain growth well, but also makes reasonable attribution of the low activation energy to the short-range rearrangement of atoms in the interface region as well.