Coating Modification Of FeSiCr Soft Magnetic Alloys Used For Multilayer Inductors

Compared with soft ferrite materials,Iron-based soft magnetic alloys have advantages in the raw material sources and prices.Because of the higher Saturation magnetic induction,it can meet the work in the higher magnetic induction intensity.In recent years,Iron-based soft magnetic alloys are widely used as Ferromagnetic material for Chip inductance components,achieving the replacement of some ferrite materials.However,the resistivity of iron-based soft magnetic alloys is several orders of magnitude lower than that of soft ferrite,causing serious loss problem in AC magnetic field.In this paper,silica insulation coatings were synthesized on the surface of FeSiCr Soft magnetic alloy powder with Polyvinyl pyrrolidone?PVP?or 3-Aminopropyltriethoxysilane?APTES?as coupling agent and tetraethyl orthosilicate?TEOS?as precursor.This method has successfully fabricated FeSiCr/SiO₂ soft magnetic composite material with low loss at high frequency.The Phase,composition and Surface microstructure were characterized with XRD,SEM,EDS,FTIR and XPS.The Resistivity and magnetic properties were characterized with Four-probe resistivity meter,Impedance meter and B-H analyzer.The results are as follows.With Polyvinyl pyrrolidone?PVP?or 3-Aminopropyltriethoxysilane?APTES?as coupling agent and tetraethyl orthosilicate?TEOS?as precursor,a flocculent amorphous silica can be successfully coated on the surface of the FeSiCr soft magnetic alloy powder.The Insulation can ensure a complete structure and will not be destroyed under the pressure of 600MPa.After the coating treatment,the permeability of the materials decreases and the resistivity increases significantly.Also,the power loss at high frequency drops and the quality factor is improved.At the same time,a constant permeability region can be obtained in the high frequency band of 1MHz to 10MHz.PVP and ATPES perform different mechanism about the surface modification,resulting in the different surface structure of the coated product.When PVP is used as the coupling agent,the coated product is nano-sized SiO₂ spherical particles.When ATPES is used,the coating product is a smooth shell-like structure.ATPES performs better than PVP in the performance of the modified function.The addition amount of the coating agent and its addition method have an important effect on the surface microstructure and magnetic properties of the coating product.When PVP is used as the coupling agent,the optimum amount of TEOS was 12ml.When ATPES is used,the optimum amount of TEOS was 10ml.Under the condition,the coating product achieves the most uniform and dense state,which has high permeability,low power loss at high frequency and high quality factor.Add the coating agent step by step can further enhance the permeability and quality factor,improving the magnetic properties of the materials.Increasing the heat treatment temperature can release the internal stress of the materials and adjust the magnetic domain structure.The permeability and quality factor of FeSiCr/SiO₂ increase with the heat treatment temperature increasing.But excessive temperature will damage the SiO₂ shell,resulting in a sharp decline in resistivity and increased magnetic losses.The optimum heat treatment temperature for the FeSiCr/SiO₂materials is 800?.