The role of microstructural evolution during spark plasma sintering on the soft magnetic and electronic properties of a CoFe–Al2O3 soft magnetic composite

Abstract

For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic polarization and high electrical resistivity are needed. This work aimed at the development of a soft magnetic composite synthesized via spark plasma sintering with both high saturation magnetic polarization and high electrical resistivity for efficient soft magnetic cores. CoFe powder particles coated with an insulating layer of Al2O3 were used as feedstock material to improve the electrical resistivity while retaining high saturation magnetic polarization. By maintaining a continuous non-magnetic Al2O3 phase throughout the material, both a high saturation magnetic polarization, above 1.5 T, and high electrical resistivity, above 100 μΩ·m, were achieved. Through microstructural characterization of samples consolidated at various temperatures, the role of microstructural evolution on the magnetic and electronic properties of the composite was elucidated. Upon consolidation at relatively high temperature, the CoFe was to found plastically deform and flow into the Al2O3 phase at the particle boundaries and this phenomenon was attributed to low resistivity in the composite. In contrast, at lower consolidation temperatures, perforation of the Al2O3 phase was not observed and a high electrical resistivity was achieved, while maintaining a high magnetic polarization, ideal for more efficient soft magnetic materials for transformers and inductors.

Novel Functional Soft Magnetic CoFe2O4/Fe Composites: Preparation, Characterization, and Low Core Loss

“…In recent years, more kinds of inorganic materials with insulative properties and ferromagnetic materials have been utilized as the coating layer to increase electrical resistivity because of their high thermal stability and resistivity. Inorganic materials, for example ZrO 2 , AlN, Al 2 O 3 , Cr 2 O 3 , TiO 2 , SiO 2 , MgO, and so on [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] and phosphates [ 17 ], are non-ferromagnetic, which decreases the saturation magnetization and the permeability of soft magnetic composites. Nevertheless, ferrite as an important ferromagnetic material has excellent performance, which is considered as an ideal insulating coating used in soft magnetic composites because of their high electric resistivity and low eddy current loss.…”

The Influence of Oxidation on the Magnetic, Electrical, and Mechanical Properties of Co40Fe40Yb20 Films

“…CoFe alloys are frequently used in a wide range of magnetic devices, including sensors, actuators, magnetic read heads, and magnetic random-access memory (MRAM) [ 1 , 2 , 3 ]. Magnetic tunnel junction (MTJ) is the primary memory component of MRAM (MTJ).…”