Changes in crystallite size and microstrains of hematite derived from the thermal decomposition of synthetic akaganeite

The thermal decomposition of akaganeite, β-FeOOH, in air is studied. The structural properties of the dehydroxylation product, identified as hematite, are determined at different temperatures. From the results on crystallite size and microstrains, a change of crystallite shape has been shown to occur in the range of temperatures of 300 to 485°C. A marked increase in crystallite size and a diminution in microstrains is observed at 525°C. This change is related to the occurrence of an exothermic peak in the DTA and DSC curves of akaganeite at about 512°C. The peak is thus ascribed to a recrystallization process of hematite. Electron micrographs support the most relevant observations of changes in particle size and shape.