Synthesis of Hexagonal Ferrites by Citric Complex Method

Various hexagonal ferrites, which include hard and soft ferrites, were prepared by citric complex method. High purity reagent of strontium carbonate, iron (III) nitrate ennnahydrate, cobalt (II) nitrate hexahydrate and lanthanum oxide were used as starting materials. Prepared aqueous solution was heated for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens and then heated at temperature range between 1023K and 1523K in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction. Scanning Electron Microscope was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by using a vibration sample magnetometer. Magnetization and coercive force were measured. In the case of M-type ferrite, M-type barium and strontium ferrites were formed at vary low temperature relative to by conventional synthesis. The lanthanum and cobalt substituted M-type strontium ferrite ultra fine powders prepared by citric complex method showed extremely large coercive force.