Enhanced Magnetic Properties of Hot-Pressed Fe-Based Nanocrystalline Powder Cores With Low-Melted Glass-Modified Insulating

Low-melted nano-sized Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glasses have been used to modify resin-based insulating for preparing Fe-based nanocrystalline soft magnetic composites (SMCs) by hot-pressing followed by annealing. The phase transition of the ferromagnetic particles and evolution of the insulating matrix of the SMCs at various annealing temperatures have been investigated and its effect on their magnetic properties has also been discussed. Internal stresses induced by compaction have been gradually released with increased annealing temperature, thereby lowering the power losses and enhancing the frequency stability of the real part of permeability below 450 degrees C. After softening of the nano-sized glasses, the SMCs show a dense and electrically isolated microstructure with the annealing temperature reaching above 450 degrees C, which not only greatly improves the initial permeability, Vickers hardness, and density but also reduces the coercivity. Excellent magnetic properties and high-frequency performance have been realized in the developed SMCs such as high real part of permeability (similar to 78.1) with relatively high-frequency stability (similar to 5 MHz), low coercivity (similar to 2.18 Oe), and total core losses (177.8 kW/m(3) at B-m = 50 mT and f = 100 kHz).