Conversion of Conventionally Synthesized Strontium Hexaferrite Powder Into a Nano Size Powder With Enhanced Coercivity Using GTMR Method

Strontium hexaferrite nanocrystalline powder was prepared by H₂, CO and CH₄ gas heat treatment and recalcination of the conventionally synthesized powder. The conventionally synthesized strontium hexaferrite was heated in hydrogen, carbon monoxide and methane dynamic atmospheres. This resulted in a change in magnetic nature of the material from hard to soft by decomposition of hexaferrite and reduction of the resultant iron oxide to the ultraflne grains of iron. Then the resultant powders calcined at 1000degC for 1 hour to form the single phase strontium hexaferrite again but with a nanocrystalline structure due to the formation of hexaferrite crystallites on the ultraflne grains of iron. In this work, the comparative effects of these processes on the phase evolution, morphology and size of the crystallites and magnetic properties were investigated by X-Ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM and TEM) and Vibration Sample Magnetometery (VSM) techniques. The results show a good enhancement in the magnetic properties particularly coercivity by applying this new method on the hexaferrite powder. Finally, the effect of milling process before recalcination on the magnetic properties has been investigated which shows a more significant improvement in the intrinsic coercivity of the initial material.