Investigation of the Influence of Raw Material Fe₂O₃ on the Magnetic Properties of Sr-ferrite Magnets

Abstract

The influence of specific surface area (SSA) of Fe₂O₃ was investigated while evaluating the raw material of Sr ferrite preparation. For hard ferrite magnet, SSA of Fe₂O₃ was found markedly affects the grain growth and the magnetic properties. Increasing of SSA of Fe₂O₃ resulted in the increase of remanence (B_R) and (BH)_max, but also causes a decline in intrinsic coercive force (_iH_C). The SSA of Fe₂O₃ is most important factor in determining the reactivity of the ferrite specimens during calcinations and sintering processes. A larger SSA promotes reactivity, which results in larger grain size of either calcined or sintered powder, consequently larger B_R and smaller _iH_C were achieved, whereas, the opposite trend was observed for small SSA of Fe₂O₃. Results are also confirmed that, when less impurity in Fe₂O₃, the microstructure and magnetic properties of Sr-ferrite have smaller sensitivity to the SSA of Fe₂O₃. As found in this study, well control of raw material Fe₂O₃ is shown to be very critical in tailoring suitable B_R and _iH_C for customized Sr-ferrite manufacturing process.