FeSiCr@NiZn SMCs with ultra-low core losses, high resistivity for high frequency applications

Abstract

Soft magnetic composites (SMCs) are widely applied in electronic devices and components, such as inductors, as they possess the highly-saturated magnetization M s of metallic materials and the highly-insulating characteristics of non-metals. However, with the development of electronic systems that require high-frequency operation, high-energy-transfer efficiency, and miniaturization, the suppression of core losses P cv in their SMCs remains a considerable challenge. Herein, we explore ways to improve the frequency dependence of core losses by using various concentrations of NiZn ferrite (0.0–5.0 wt%) to coat FeSiCr magnetic powders. The microstructural, magnetic, dielectric, and core loss performances of FeSiCr@NiZn SMCs are investigated in detail. Energy dispersive X-Ray spectroscopy (EDS) mapping confirmed that the FeSiCr magnetic powders were able to be well coated with NiZn ferrite. Core loss separation method was utilized to calculate hysteresis losses P h and eddy current losses P e from 25 to 800 kHz at 10 mT and 25 °C. With increasing NiZn ferrite concentration, both P cv and P h initially decreased and subsequently increased, while P e decreased monotonically. The sample with 3.0 wt% NiZn ferrite had the best overall performance: saturation magnetization M s = 157 emu/g, coercive force H c = 4.6 Oe, effective permeability μ e = 60, resistivity ρ = 1.25 × 10 4 Ω∙m, and core losses P cv = 38 mW/cm 3 (at 800 kHz, 10 mT, and 25 °C). The excellent electromagnetic properties of these novel FeSiCr@NiZn SMCs give them enormous application potential in the fields of power transmission and conversion. • EDS mapping confirmed that the FeSiCr powders were well coated with NiZn ferrite. • The high-resistance layer of NiZn ferrite are beneficial for the reduction of P cv . • FSC0NZ possessed optimum P cv = 38 mW/cm 3 (at 800 kHz, 10 mT, and 25 °C).