Achieving Ultra‐Low Megahertz Loss in Nanocrystalline Magnetic Powder Cores via Alloy Design and a Self‐Healing Organic–Inorganic‐Derived Hybrid Insulating Layer
Cheng Chen, Changlong Jin, Yanzhou Fan, Zhijun Guo, Jifeng Zhou, Qianzi Yang, Fan Hu, Qiang Luo, Qianqian Wang, Xingdu Fan, Baolong ShenABSTRACT
High‐frequency power electronics demand soft magnetic core materials with high saturation magnetic flux density ( B s ) and ultra‐low high‐frequency core loss ( P cv ) in the megahertz range. Here, we design a Fe 74.3 P 3.9 Si 7.6 B 9.5 C 1.9 Nb 2 Cu 0.8 nanocrystalline alloy with excellent soft magnetic properties and prepare fully amorphous spherical powders via gas atomization. A self‐healing organic–inorganic‐derived hybrid insulating layer composed of FePO 4 /B 2 O 3 /epoxy resin is constructed through phosphoric acid passivation followed by in situ triethyl borate (TEB) coating. During subsequent annealing, the low‐melting‐point B 2 O 3 melt heals microcracks, forming a continuous and homogeneous interfacial layer that synergistically suppresses hysteresis, eddy‐current, and excess losses. The optimized TEB‐2 magnetic powder core exhibits exceptional comprehensive performance: an ultra‐low P cv of 265 mW/cm 3 at 0.1 T and 100 kHz (8.6 W/cm 3 at 0.1 T and 1 MHz), an effective B s of 1.00 T, an effective permeability ( µ e ) of 51 at 1 MHz, and a DC‐bias of 48% at 100 Oe. Finite‑element simulations corroborate that the hybrid coating homogenizes local flux distribution and suppresses interfacial flux perturbations, directly accounting for the reduced excess loss. This work demonstrates a synergistic strategy combining alloy design and interface engineering, offering theoretical insights and experimental guidance for developing nanocrystalline magnetic powder cores for next‐generation high‐frequency power devices.