Yasunobu Yamada

Novel

Fe-based glassy alloys with both high saturation magnetization and low magnetic anisotropy have attracted interest recently , and we have succeeded in developing novel glassy Fe_(97-x-y)P_xB_yNb₂Cr₁ (x=5 -13, y=7-15) alloys for an inductor material with high corrosion resistance by added Cr is 1 at%. The glassy alloy series of Fe_(97-x-y)P_xB_yNb₂Cr (x=5-13, y=7-15) have high glass-forming ability with wide range super-cooled liquid region of 29-37 K, large critical thickness of 110-150 ¿m, and low coercivity of 2.5-3.1 A/m caused by the structural homogeneity. The Fe₇₇P₇B₁₃Nb₂Cr₁ glassy alloy exhibits the largest critical thickness of 150 ¿m related to the wide super-cooled liquid region of 36 K and the high saturation magnetic flux density (Bs) of 1.3 T, both of which are higher than those of the conventional amorphous Fe₇₅Si₁₀B₁₂Cr₃ alloy. The Fe-P-B-Nb-Cr powder/resin composite core has much lower core loss of 650 kW/m³ which is approximately 1/3 lower than the conventional amorphous Fe-Si-B-Cr powder/resin composite core annealed at 623 K. Additionally, The Fe-P-B-Nb-Cr glassy alloy has higher corrosion resistance than other system glassy metal of Fe-Si-B-Nb-Cr by having a thick chromium passivation layer. the optimum annealing temperature of 623 K for these glassy alloys is lower than that (723 K) for the ordinary Fe-Si-B-Cr amorphous alloy, which is a significant advantage for the efficiency in mass production of inductor core using soft magnetic glassy alloy powder.

{\hbox {Fe}}_{(97-{\rm x-y})}{\hbox {P}}_{\rm x}{\hbox {B}}_{\rm y}{\hbox {Nb}}_{2}{\hbox {Cr}}_{1}

The inductor for a power supply is expected to have higher efficiency and capability of dealing satisfactorily with large current. Additionally, high corrosion resistance characteristics are also required for commercial inductors in practical use of. Thereby, we focused on Fe-based glassy metal alloys with both high magnetization and low magnetic anisotropy ［1］, and developed the novel glassy metal alloys with a chemical composition Fe97-x-yPxByNb2Cr1. In this glassy metal alloy, 1 at % Cr is the optimum composition for the realization of higher corrosion resistance as well as a high magnetic flux density. The glassy Fe97-x-yPxByNb2Cr1 (x=5-13, y=7-15) alloy exhibits the high glass-forming ability leading to the large thickness of 110-150 μm and low coercive force of 2.5-3.1 A/m due to higher structural homogeneity in wide range of composition. The large critical thickness of this alloy should be caused by the high glass-forming ability (GFA) due to the existence of the super cooled liquid region (Tx) of roughly 30 K. Therefore a Fe77P7B13Nb2Cr1 powder/resin composite core displays a much lower core loss of 650 W/m3 than the conventional amorphous Fe75Si10B12Cr3 powder/resin composite core by approximately 1/3.

Glassy Alloys With High Magnetization and Low Loss Characteristics for Inductor Core Materials

Effects of P content in amorphous and nanocrystalline FeSiBPCu soft magnetic alloys were investigated by comparing the corresponding change in the saturation magnetic flux density and coercivity. Ribbons were prepared using a high induction melting and melt spinning method. As-quenched Fe_85.5Si₂B₁₀P_1.5Cu₁ alloy consisted of minor crystalline phase. With an increase of P content, the glass forming ability was enhanced. The decrease in the saturation magnetic flux density associated with increased P content, was mainly ascribed to the decrease in Fe content. Nanocrystalline Fe_87-xSi₂B₁₀P_xCu₁ alloys exhibited higher saturation magnetic flux density and lower coercivity, when x was >2 at%. The best soft magnetic performance was obtained at x = 2 at%, where the saturation magnetic flux density was 1.87 T. The coercivity was decreased with P content, indicating that the size of α-Fe grains became smaller with the increase of P content.

FePBNbCr Soft Magnetic Glassy Alloys “SENNTIX” with Low Loss Characteristics for Commercial Inductor Cores

Low loss, high flux density powder cores were successfully developed by compacting Ni-Zn ferrite plated Fe-Si powder. The ferrite-plated powder cores annealed at 150 and 400 /spl deg/C exhibited higher magnetic permeability than those of resin-coated powder cores annealed at the same temperatures. This higher permeability is attributed to a larger magnetic component in the compact using ferrite layer as insulation layer instead of non-magnetic silicone resin. The ferrite-coated powder cores showed low total power loss attributed to their high magnetic flux density compared to the resin-coated powder cores. These results indicate that the ferrite-coated cores are very promising for magnetic cores used in powder choke coils.