Study of the Effect of Specific Surface Area and Purity of Fe2O3 on the Magnetic Properties of Sr-Hexaferrites

The effect of specific surface area (SSA) and the purity of Fe 2 O 3 were investigated while evaluating the raw material of Sr-hexaferrite preparation. For anisotropic hard ferrite, both SSA and purity of Fe 2 O 3 were found, which markedly affect the grain growth and the magnetic properties. Increase of SSA in Fe 2 O 3 resulted in the increase in remanence (B R ) and (BH) max , but also causes a decline in intrinsic coercive force (iH C ). It appears that the most important parameters for determining the reactivity of the ferrite specimens during calcinations and sintering processes are the SSA of Fe2O3. A larger SSA promotes reactivity, which results in a larger grain size of calcined and sintered powder, and consequently, larger B R and smaller iH C were obtained, whereas the opposite trend was observed for small SSA of Fe 2 O 3 . The purity of Fe 2 O 3 is known to impact the properties of Sr-ferrite. Uniform grain sizes of calcined and sintered powders are both observed, while high purity Fe 2 O 3 was used. Results are confirmed that, when less impurity, the microstructure and the magnetic properties of Sr-ferrite have smaller sensitivity to the SSA of Fe 2 O 3 . As found in this paper, well control of SSA and purity of raw material Fe 2 O 3 are shown to be very critical in tailoring suitable B R and iH C for a customized Sr-ferrite manufacturing process.