Synthesis of Iron Nitride-Based Magnetic Powder with Oxide Shell by Gas-Solid Reaction and its Application to Magnetic Powder Core

Cobalt-included iron nitride-based powder with a thin oxide shell was fabricated and compacted into a magnetic powder core, and its core loss and permeability are reported. In order to maximize performance in the frequency band toward MHz, much attention is paid for the characteristics of inductors using materials with high saturation magnetic flux density as the ideal limit when soft magnetic properties and linearity are guaranteed. As a soft magnetic material with high saturation magnetization, an α″-Fe16N2 powder whose nitrogen (N) is partially replaced by carbon (C) is expected. Regarding the possibility for high-frequency operation, an insulator shell on the surface of magnetic powder is effective to suppress eddy current. In this study, we establish a continuous gas-solid reaction process to synthesize the iron nitride-based magnetic powder which N and C penetrated into the Fe-based body-centered cubic crystallite as well as forming a thin oxide shell. Furthermore, we fabricated a magnetic powder core using this powder and discuss core loss and permeability.