Effects of Surface Oxidation on the Magnetic Properties of Fe-Based Amorphous Metal Powder Made by Atomization Methods

The demand for soft magnetic amorphous metal powders with high saturation magnetization values and low energy loss has increased to achieve high-performance inductors for mobile electronic devices. In this study, Fe-based Fe_92.3Si_3.5B_3.0C_0.7P_0.5 (wt.%) amorphous metal powders were prepared using different atomization methods for controlling the surface oxidation of the metal alloy powder. Conventional high-pressure water atomization and the newly developed high-speed water screen atomization methods were used for preparation. Regardless of the preparation methods, both alloy powders were amorphous, and their magnetic flux density (Bs) values were more than 165 emu/g. Compared to the powders from the conventional high-pressure water atomization method, the amorphous metal powder manufactured using the high-speed water screen atomization process had lower eddy current loss because of the formation of a thin and uniform oxide layer. Furthermore, the magnetic properties of the consolidated magnetic cores fabricated with the amorphous powders produced by the high-speed water screen atomization method using compact-pressing techniques were characterized. Magnetic powders with fewer surface oxidation layers exhibited increased initial permeability and a smaller coercive field, leading to a lower core loss value. The magnetic core made from Fe_92.3Si_3.5B_3.0C_0.7P_0.5 (wt.%) amorphous powder with an oxide content of 0.12 (wt.%) using the high-speed water screen atomization method exhibited an initial permeability of 25 in the frequency range up to 5 MHz, and a loss of 237 mW/cm³ with B_m = \(0.2\,{\text{T}}\) at 1 MHz.

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