THE THERMAL-STABILITY OF NANOCRYSTALLINE MAGHEMITE FE2O3

Nanocrystalline maghemite Fe2O3 was prepared by a wet chemical method. The thermal stability of this material has been investigated by using differential thermal analysis (DTA) measurements and x-ray diffractio n analyses. One exothermic peak without weight loss appears irreversib ly on the DTA curve. It was confirmed for the first time that this exo thermic peak corresponds completely to the maghemite-to-hematite (gamm a-to-alpha) structural phase transition. The nanocrystalline maghemite Fe2O3 particles grow very slowly when the temperature is lower than t he range of the exothermic peak; whereas, during and after the transit ion, the nanocrystalline hematite Fe2O3 particles grow rapidly with in creasing temperature. Moreover, the transition temperature of nanocrys talline maghemite Fe2O3 is higher than that of the coarse-grained coun terpart. In this paper, the authors have also suggested some prelimina ry physical interpretations of the experimental results.