Microstructure evolution and soft magnetic properties of Fe-based nanocrystalline soft magnetic composites coated with lubricant

Here, the influence of zinc stearate on the microstructure and soft magnetic properties of the Finemet nanocrystalline soft magnetic composites (NSMCs) was systematically investigated. The results demon-strate that the core loss (Pcv) decreases and the effective permeability (le) increases of the NSMCs with increasing zinc stearate from 0 wt% to 2.0 wt%, which can be attributed to the reduction of residual stress during compaction. Further increasing zinc stearate up to 3.0 wt%, the Pcv increases sharply, while the le shows a decreasing trend. It can be considered that the addition of excess lubricant decomposes to CO2 during annealing, which deteriorates the magnetic properties. After annealing at 560 degrees C, a thin hybrid layer of only about 53.6 nm containing iron phosphate, ZnO, and SiO2 is formed in the NSMCs with 2.0 wt% zinc stearate, which exhibits excellent soft magnetic properties such as low Pcv of 174 kW/m3 and high le of 66.7 at Bm = 0.1 T for 50 kHz. In addition, loss separation has been carried out and suggests that the addition of lubricant mainly affects hysteresis loss in the total energy loss of NSMCs. (c) 2023 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.

Automated summary

The influence of zinc stearate on the microstructure and soft magnetic properties of Finemet nanocrystalline soft magnetic composites (NSMCs) was investigated. It was found that increasing the zinc stearate content led to a decrease in core loss and an increase in effective permeability, which can be attributed to the reduction of residual stress. However, excessive addition of zinc stearate resulted in a sharp increase in core loss and a decrease in effective permeability due to decomposition during annealing. After annealing, a thin hybrid layer containing iron phosphate, ZnO, and SiO2 was formed in the NSMCs with 2.0 wt% zinc stearate, exhibiting excellent soft magnetic properties.