Preparation of strontium hexaferrite nano-crystalline powder by carbon monoxide heat treatment and re-calcination from conventionally synthesized powder

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 degrees C for 1 h. 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 degrees C with 20 cm(3)/min flow for 0.5 h. The resultant powder was then calcined at 900 and 1000 degrees C for 1 h. The single-phase strontium hexaferrite nano-crystalline powder was finally obtained after calcination at 1000 degrees C. The phase identification of the powders was recorded by an X-ray diffractometer (XRD) with Cu K alpha 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. (C) 2008 Elsevier B.V. All rights reserved.