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Conventional Ceramic Reaction Methodology has been utilized for the preparation of M-type hexagonal ferrites of Sr0.35La0.40Ca0.25Fe11.6Co0.4O19 magnets. X-ray diffraction has been performed for phase determination of the magnetic powders. At calcination temperatures ranging from 1220 to 1330 ∘C, the synchronize compost of the magnetic powders comprised of M-type hexagonal ferrites together with a small amount of impurity phase such as α-Fe2O3 were co-existed. At calcination temperature above 1270 ∘C, single-phase M-type hexaferrites can be obtained. The particles seemed to be in a hexagonal plate-like mould which spread-out homogeneously were examined by field emission scanning electron microscopy. The magnetic edibility of the magnetic powders was intended by permanent magnetic measurement test equipment vibrating sample magnetometer. Magnetic properties, such as specific saturation magnetization, coercivity and remanence were temperature-dependent. However, with the increase of sintering temperature, i.e. above 1270 ∘C, saturation magnetization was increased while the coercivity showed reversed order. [ABSTRACT FROM AUTHOR]

Abstract: In this work strontium hexaferrite nano-crystalline powders were prepared by carbon monoxide heat treatment and re-calcination from conventionally synthesized powder. First strontium hexaferrite was obtained by the conventional route with calcination of strontium carbonate and hematite at 1100°C for 1h. Then strontium hexaferrite was isothermally subjected to carbon monoxide dynamic atmosphere at various temperatures and flows for different times. Optimum carbon monoxide heat treatment was achieved at 850°C with 20cm3/min flow for 0.5h. The resultant powder was then calcined at 900 and 1000°C for 1h. The single-phase strontium hexaferrite nano-crystalline powder was finally obtained after calcination at 1000°C. The phase identification of the powders was recorded by an X-ray diffractometer (XRD) with Cu Kα radiation. Morphology and size of the particles were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The magnetic properties were also measured by a vibration sample magnetometer (VSM). The results show a good enhancement in the coercivity by applying this method on the hexaferrite powder. [Copyright &y& Elsevier]