Structure and magnetic properties of ZrO2-coated Fe powders and Fe/ZrO2 soft magnetic composites

Fe particles were coated with ZrO₂ nanopowders using mechanical milling method combined with high temperature recovery annealing process. The effect of milling time on particle size, phase structure and magnetic properties of the core-shell structure powders was studied. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) revealed that the surfaces of the composite powders comprised thin and uniform layers of ZrO₂ insulating powders after milling. Also, the SEM images showed the morphology of micro-cellular structured compacts with cell-body of Fe particles and indicated that Fe particles were well separated and insulated by thin ZrO₂ layers. The Fe/ZrO₂ soft magnetic composites displayed much higher electrical resistivity, lower core loss than that of the pure Fe powder cores without ZrO₂ layers at medium and high frequencies. The preparation method of ZrO₂-insulated Fe powders provides a promising method to reduce the core loss and improve the magnetic properties for soft magnetic composite materials.