Barium hexaferrite (BaFe12O19) as a ceramic magnet with outstanding magnetic properties has various applications in telecommunication, data storage devices and electronics. Various non-conventional methods like sol-gel, co-precipitation and hydrothermal have been employed to synthesize such a magnets. In this work, barium hexaferrite particles were prepared by self-propagating high temperature synthesis method using iron, iron oxide and barium nitrate as starting materials. Fet/Ba molar ratio was adjusted to 9 with different ratios of Fe/Fe2O3. Effect of iron content on the phase constitution and the reactions occurred during SHS and annealing treatment were investigated. XRD, DTA/TGA, VSM and SEM techniques were applied to characterize the resultant powders. Heat released from oxidation of iron sustained the synthesis process in a propagating manner. The oxygen sources for oxidation of iron were 1. air ( external source) and 2. barium nitrate which acted as an internal oxidizing agent. SHS process resulted in small content of barium hexaferrite, only in sample with Fe/Fe2O3=1.3. SHS process in sample with
Fe/ Fe2O3=2 had a good speed and combustion front had a non-stop movement. XRD results showed this sample contained barium monoferrite, wustite, magnetite and hematite. DTA trace of sample with Fe/ Fe2O3=2 revealed an exothermic peak at 828oC which may be corresponded to the formation of barium hexaferrite. Annealing of SHS products resulted in gradual formation of barium hexaferrite phase. The results indicated that the content of barium hexaferrite magnetic phase increased by increasing the annealing temperature and in 1150oC hematite did not exist but small amount of barium monoferrite was still present. It can be concluded that for achieving single phase of barium hexaferrite, higher Fe/Ba molar ratio should be used. Scanning Electron Microscopy (SEM) showed hexagonal particles with particle size of 1 to 2 µm in sample annealed at 1150oC for 2 h in air. Saturation magnetization and coercivity were measured 54.7 emu/g and 1.7 kOe, respectively for sample annealed at 1050oC for 2 h in air.
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