Enhanced AC magnetic properties of Fe-based soft magnetic composites coated with an electrically insulated SiO_2-ZrO_2 layer

摘要

Insulating Fe@SiO_2-ZrO_2 (FSZ) composite powders were synthesized by a co-precipitation method and the corresponding soft magnetic composites (SMCs) were fabricated with the powder metallurgy technique. The FSZ powders fabricated with 80 mmol/L tetraethyl orthosilicate and 20-40 mmol/L ZrOCl_2. 8H_2O exhibits a dense and uniform SiO_2-ZrO_2 insulating layer with high Si-O and Zr-O binding energies, high saturation magnetization (M_s > 200.4 emu/g), and low coercivity (H_(ci), < 45.9 Oe). Compared with Fe@SiO_2 SMCs, Fe@SiO_2-ZrO_2 SMCs have a higher resistivity of 941.9-984.2 μΩ, and most of the eddy current losses are suppressed, contributing to superior alternating current magnetic properties, including a flat frequency character up to 1 MHz, lower core loss (P_s) of 17.9-19.2 W/kg (20 mT/100 kHz) and high permeability (μ_m) of 64-73. Electron probe microanalysis measurements confirmed that Fe powders are fully separated by a thin insulating layer composed of a large amount of SiO_2 and a small fraction of ZrO_2, which displays outstanding pressure resistance and thermal stability characteristics and contributes to the fabrication of SMCs with high resistivity and low core loss.