Studies on the reaction between strontium carbonate and iron(III) oxide

The reaction between strontium carbonate and iron(III) oxide has been studied in a system open to the atmosphere and in a vacuum. The extent of reaction was calculated from the analysis of the solid products by X-ray diffraction and, in the case of the experiments in vacuum, from the amount of carbon dioxide evolved from the system also.     In vacuum, the monoferrite SrFe2O4 results from the direct reaction of strontium carbonate and iron(III) oxide at comparatively low temperatures, while the hexaferrite SrFe12O19 is formed by the reaction of Sr2Fe2O4 with iron(III) oxide at higher temperatures. The formation of the ferrite Sr2Fe2O5 depends upon the prevailing atmosphere, since this compound was present only as an intermediate phase when the experiments were carried out in air and not in vacuum. Only three compounds of strontium, iron, and oxygen were found, namely the ferrites SrFe2O4, Sr2Fe2O5, and SrFe12O19.     The observataions appear to be explicable in terms of Tammann temperatures.