Akiri Urata

Low core losses and magnetic properties of Fe85-86Si1-2B8P4Cu1 nanocrystalline alloys with high B for power applications (invited)

Recently, the energy crisis and the continued growth in electrical power generation strongly demand minimization of wasteful energy dissipation. Magnetic core loss (W) is the main source of energy dissipation in motors and transformers. This requires the development of soft magnetic materials with low coercivity (Hc) and high magnetic flux density (B). Fe-rich Fe85-86Si1-2B8P4Cu1 (at. %) alloy ribbons made from industrial raw materials (containing some impurities) with 6 mm in width have a heteroamorphous structure containing a large number of extremely small Fe grains (less than 3 nm), resulting from the unique effects of P and Cu addition in proper amounts. Crystallization of these alloys by annealing shows a uniform precipitation of α-Fe, leading to a uniform nanocrystallized structure of α-Fe grains, 16–19 nm in size, accompanied by an intergranular amorphous layer about 1 nm in width. The wide ribbons exhibit high B of 1.82–1.85 T (at 800 A/m), almost comparable to commercial oriented Fe–3 mass% Si a...

Magnetic properties of (Fe, Co)–B–Si–Nb bulk glassy alloys with high glass-forming ability

The glass-forming ability and magnetic properties of (Fe, Co)–B–Si–Nb glassy alloys have been investigated. The maximum diameter for the formation of a glassy alloy rod was 2.0mm for Fe72B20Si4Nb4 and 4.0mm for (Fe0.5Co0.5)72B20Si4Nb4. A number of local-ordered regions are recognized in Fe72B20Si4Nb4 bulk glassy alloy by high-resolution transmission electron microscopy. However, no local-ordered regions are observed in (Fe0.5Co0.5)72B20Si4Nb4 bulk glassy alloy. Saturation magnetization, coercive force, and maximum permeability were 1.14T, 1.5A∕m, and 32 000, respectively, for the (Fe0.6Co0.4)72B20Si4Nb4 bulk glassy alloy.

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 glass forming ability and magnetic properties of a Co–B–Si–Nb glassy alloy have been investigated. The maximum rod diameters for the formation of a glassy phase were 1.5mm for Co70B20Si8Nb2 and 3mm for Co70B22Si6Nb4. Zero-magnetostriction bulk metallic glass samples of (Co0.952Fe0.058)70B20Si8Nb2 were prepared in cylindrical form with a diameter of 1.5mm and in ring form with a thickness of 0.5mm. The (Co0.952Fe0.058)70B20Si8Nb2 glassy alloy samples exhibited a high glass forming ability and good soft magnetic properties, i.e., a saturation magnetization of 0.6T, a low coercivity within 0.1–0.2A∕m, and a high permeability of 104 000 at a frequency of 1kHz and zero magnetostriction. The success of the synthesis of the zero-magnetostriction Co–Fe–B–Si–Nb glassy alloy with good soft magnetic properties and a high glass forming ability is promising for the future development of sensitive magnetic sensors.

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

The effect of replacement Si by P on the soft magnetic and structural properties of nanocrystalline Fe-Si-B-P-Cu alloys has been investigated. The nanocrystalline Fe83.3SiXB8P8−XCu0.7 (X = 0, 2, 4, 6) alloy ribbons consist of precipitated α-Fe phase and residual amorphous phase, and initial permeability of these alloy ribbons are enhanced with decreasing Si content. In particular, the nanocrystalline Fe83.3B8P8Cu0.7 (X = 0) alloy has both low core loss of 1.4 W/kg at 1.0 T – 50 Hz and high saturation magnetic flux density of 1.70 T. In addition, this alloy exhibits the most favorable nanocrystalline structure containing the homogeneously precipitated α-Fe grains with 14 nm in mean diameter. Therefore, it can be concluded that the soft magnetic properties and nanostructure of Fe-Si-B-P-Cu alloys are strongly affected by Si and P content. The Fe83.3B8P8Cu0.7 alloy with low core loss and high saturation magnetic flux density compared with a Fe amorphous alloy is suitable for a magnetic core material in elect...

Magnetic properties of Co–Fe–B–Si–Nb bulk glassy alloy with zero magnetostriction

The inductor in a power supply is required to be capable of dealing satisfactorily with the high-current supply and to improve the power loss characteristic. A novel glassy metal powder with a chemical composition Fe77P7B13Nb3 features both a high saturated magnetic flux density of 1.3 T and a low coercive force of 2.0 A/m, which has a stable amorphous structure suitable for glassy metal composite cores. Hence there is no magnetic saturation even under a high-current supply, and it is confirmed to have significantly low magnetic loss resulting from the low coercive force. As a result of using the glassy metal alloy Fe77P7B13Nb3 powder in an inductor core, we have achieved improvement in power supply efficiency by up to roughly 2.0%. Moreover, the reduction in the standby power requirement by the improvement in the power supply efficiency in the low load current case, where the core loss occupies a high ratio in the entire loss, can be expected. Additionally, heat generation in a core is suppressed by usin...

Low core loss of non-Si quaternary Fe83.3B8P8Cu0.7 nanocrystalline alloy with high Bs of 1.7 T

Magnetic properties and fine structure of Fe-Si-B-P-Cu nanocrystalline alloy ribbons have been investigated. The Fe_84.8(Si,B,P)₁₄Cu_1.2 alloy ribbons using industrial materials are produced by a single-roller melt-spinning method in air. The Fe_84.8(Si,B,P)₁₄Cu_1.2 nanocrystalline alloys exhibit low coercivity H_c of 7-20 A/m in the compositional range of Si=0-2 at% and P=2-8 at% and high saturation magnetic flux density B_s of 1.80 T or more in the compositional range of P=0-4 at%. In particular, Fe_84.8Si₁B₁₀P₃Cu_1.2 nanocrystalline alloy annealed at 698 K exhibits both the high B_s of 1.82 T and the low H_c of 7.2 A/m. The iron loss <i>W</i> at 50 Hz of the Fe_84.8Si₁B₁₀P₃Cu_1.2 nanocrystalline alloy is much smaller than oriented and nonoriented magnetic steel over the maximum induction B_m range up to 1.7 T. In addition, nanocrystalline structure of the Fe_84.8Si₁B₁₀P₃Cu_1.2 alloy exhibits a homogeneous nanocrystalline structure composed of α-Fe grains with 5-20 nm in diameter even using industrial materials. Therefore, the Fe-Si-B-P-Cu nanocrystalline alloy has good soft magnetic properties and a large economical advantage of low material cost by using industrial materials.

To enhance the efficiency of a power supply circuit by the use of Fe-P-B-Nb-type ultralow loss glassy metal core

The effects of Fe content on the magnetic properties and fine structure of the nanocrystalline Fe-B-P-Cu alloys have been investigated, with the objective of enhancing their magnetic softness. The nanocrystalline Fe83.3+xB7−xP9Cu0.7 (x = 0.0–2.5) alloys annealed at 673 K consist of uniform α-Fe grains embedded in a residual amorphous phase, and the average α-Fe grain diameter decreases from 18.1 to 14.6 nm with increasing Fe content. At the same time, the saturation magnetic flux density (Bs) increases and the coercivity (Hc) decreases with increasing Fe content and the x = 1.0 alloy has a high Bs of 1.72 T and a low Hc of 2.9 A/m. At x = 2.0 or higher, however, Hc drastically deteriorates from the effect of the coarse α-Fe grains. The core loss (W) of the x = 1.0 alloy at 50 Hz-1.6 T is 0.26 W/kg, which is one-third of that for oriented magnetic steel. These results indicate that the magnetic properties and structure of nanocrystalline Fe-B-P-Cu alloys are strongly affected by Fe content.

Fe–Si–B–P–Cu Nanocrystalline Alloy Ribbons With High Saturation Magnetic Flux Density Prepared Using Industrial Materials

Nanocrystalline soft magnetic alloy powders produced by heat treating amorphous powders are expected to improve properties and miniaturize dust cores because of their low coercive force <i>Hc</i> and high saturation magnetic flux density <i>Bs</i>. By water atomization process, we successfully obtained quenched Fe-Si-B-P-Cu alloy powders with spherical particle shape. The obtained powders have different average particle sizes of 2.0, 3.0, 5.0, and 8.5 μm. After annealing at 723 K, the as-quenched alloy powders are crystallized and <i>Bs</i> of the nanocrystalline alloy powders with Fe_83.3Si₄B₈P₄Cu_0.7 and Fe_84.8Si₂B₁₀P₂Cu_1.2 exhibit high <i>Bs</i> of 1.72 and 1.76 T, respectively. Core loss characteristics of the dust cores are found to be dependent on amorphous stability of the as-quenched powders. Thus, the Fe_83.3Si₄B₈P₄Cu_0.7 nanocrystalline alloy powder with an average particle size of 3.0 μm exhibits the best core loss of 1461 kW/m³ (<i>Bm</i> = 50 mT, <i>f</i>=300 kHz).

Magnetic properties and structure of Fe83.3–85.8B7.0–4.5P9Cu0.7 nanocrystalline alloys

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.