High Performance Metallic Amorphous Magnetic Flake-based Magnetodielectric Inductors

TL;DR

This paper reports on the preparation of high aspect ratio FeSi-based metallic amorphous flakes and their use in magnetodielectric composites, demonstrating increased permeability with higher flake aspect ratios for high-frequency applications.

Contribution

It introduces a method to produce high aspect ratio FeSi amorphous flakes and shows how their incorporation enhances composite permeability at high frequencies.

Findings

Composite permeability nearly tripled with increased flake aspect ratio.

Permeability approached 10 at 0.1 GHz for high aspect ratio flakes.

Flake aspect ratio significantly influences magnetic properties of composites.

Abstract

Flake-shaped FeSi-based metallic amorphous alloy particles, having an aspect ratio as high as 175 to 1, were prepared by ball milling gas atomized amorphous powders of an effective diameter of 20 micrometers. The starting powder had a saturation magnetic flux density, Bs, of 1.5 T and a coercivity, Hc, of 94 A/m. The aspect ratio of the flakes, as well as their magnetic properties, were controlled by milling process parameters, such as duration, speed, and the type, mass and diameter of the milling balls. To minimize the oxidation of the charge, the powders were handled in an argon gas-purged glove box, milled in toluene, and subsequently dried in vacuo. Subsequently, soft magnetodielectric composites were prepared by suspending and aligning the FeSi-based powders in paraffin wax or epoxy resin. The composites were then pressed into toroids for measurements of their high frequency complex permeability by a vector network analyzer. The influence of the flake aspect ratio and volume loading fraction on the permeability of the composites were investigated. Results indicate that the composite permeability increases with the flake aspect ratio. For example, for a given loading factor of 30 vol.%, the composite permeability at 0.1 GHz nearly tripled and approached the value of 10 by increasing the aspect ratio of the FeSi-based inclusions from 1 (spheres) to greater than 175 to 1 (flakes).