MICROSTRUCTURAL AND MICROANALYTICAL EXAMINATIONS OF PARTIALLY REDUCEDDOPED WUSTITES

In this paper we report results on microstructural and compositional c haracterization of (Fe1-x-yCay)O, (Re1-x-yMny)O and (Fe1-x-yMgy)O wust ites and their reduction behaviour using optical, scanning and transmi ssion electron microscopy and X-ray microanalysis. The microstructure of mangano- and magnesio-wustites does not show any significant differ ences when compared to FeO. This is due to the complete solubility of Mn and Mg in FeO and to small differences in ionic sizes between iron and these elements. In contrast, due to significant differences betwee n iron and calcium, the microstructure of calcio-wustite consists of s tacking faults in an ordered matrix. The density of the stacking fault s increases with respect to Ca addition, up to about 1.5 wt% of Ca. Fu rther addition of Ca atoms results in the precipitation of CaFe5O7 cal cium ferrite plates as a consequence of low Ca solubility in FeO and i ts segregation to the stacking faults.