Structural analysis of co-precipitated Sr1-xLaxFe12-xCoxO19 powders

Sr1-xLaxFe12-xCoxO19 (x=0-0.4) powders produced by chemical co-precipitation were investigated by Moessbauer spectrometry and X-ray diffraction. The results show that the powders are not single hexagonal M-type phase, (La,Sr)(Fe,Co)O3-δ (mainly) and (Co,Fe)Fe2O4 (traces) being present in the substituted powders, with a proportion that increases with x. The Moessbauer spectra were fitted with a model that accounts for the presence of the secondary phases. The interpretation of the Moessbauer data shows that in the hexagonal M-type phase, La3+ and Co2+ are substituted for Sr2+ and Fe3+ respectively, with a content that is lower than the nominal content, due to the formation of the secondary phases