The formation of strontium hexaferrite SrFe12O19from pure iron oxide and strontium carbonate

The formation of strontium hexaferrite SRFE12O19from pure iron oxide and strontium carbonate has been studied by means of dynamic high temperature X-ray diffraction, thermal analysis, and thermogravimetry. The formation in air passes through two endothermal reactions: SrCo3+6α-Fe2O3+(0.5-x) O2→ SrCo3+5.5α-Fe2O3+CO2(A) SrFeO3-x+5.5α-Fe2O3→ SrFe12O19+(0.5-x) O2(B) The solid state reaction of the formation of the perovskite SrFeO3-xstarts between 660 C (0.13°/min) and 730 C (20°/min) depending on the heating rate. Above 810 C or 1000 C, resp., the perovskite reacts with the excess iron oxide forming the hexaferrite. During the process a part of the iron becomes tetravalent and is again reduced into the trivalent state. The phase Sr7Fe10O22or Sr4Fe6O13, resp., observed in quenched samples could not be detected during the formation in air.