SrFe12O19 as an impurity in perovskite-type ferrites

A decrease of oxygen content in SrFe12O19 and its subsequent decomposition were studied at 750-950 degrees C by coulometric titration. The lowest oxygen content that strontium hexaferrite endures is about 18.5. Further oxygen removal from oxide lead to its reductive decomposition with the formation of Fe3O4 and Sr4Fe6O13+delta. The stability limits of SrFe12O19 under reducing conditions was determined. The continuation of the reductive titration was shown to result in the transformation Fe3O4 -> Fe1-xO followed by Fe1-xO -> Fe. The significant release of oxygen during stepwise decomposition can be considered as a specific characteristic of SrFe12O19. It is argued that the double stepwise fall, which is often observed on oxygen content isotherms of perovskite-type ferrites, indicates the presence of SrFe12O19 impurity. (C) 2020 Elsevier B.V. All rights reserved.