Soft magnetic materials with high operating frequency and low power loss are crucial for electricity transmission and utilization. However, finding an effective method to improve the operating frequency while minimizing power loss in these materials remains a significant challenge. Herein, we synthesized the (Y1−xSmx)2Fe14B compounds and introduced nitrogen atoms into their interstitial crystal sites via the gas–solid reaction, remarkably improving their operating frequency and reducing power loss. For the compounds with x = 0.15, the operating frequency increased from 1.7 to 5.5 MHz, with the imaginary part of relative permeability decreased from 6.1 to 1.6. The power loss decreased from to , and loss separation indicated that eddy current loss was significantly suppressed by nitriding from to . The conductivity decreased by approximately 43% by nitriding, from 9380.9 to 5359.0 S/m. These results demonstrate that tuning power loss through nitrogenation of rare-earth transition metal intermetallic compounds is an effective method for developing new high-frequency and low power loss soft magnetic materials.
I. INTRODUCTION
Nowadays, the efficiency of electricity transmission and utilization is increasingly emphasized. High operating frequency, high power density, and miniaturization have become critical characteristics of power electronic devices.1–4 In this context, soft magnetic materials (SMMs) with high operating frequency and low power loss as important part of power electronic devices have become more essential.5–8 However, neither traditional Fe-based soft magnetic alloys nor soft magnetic ferrites can be used in power electronic devices to achieve high operating frequency and miniaturization due to their large high-frequency power loss and low power density.9–15 Therefore, there is an urgent need to develop new soft magnetic materials with low power loss and higher operating frequencies to meet the demands of modern power electronic devices.
Over a long period, the primary research focus on rare-earth transition metal intermetallic compounds has been the search for finding permanent magnetic materials due to their high saturation magnetization and strong magnetocrystalline anisotropy.16–22 However, rare-earth magnetic materials exhibiting planar anisotropy have been largely neglected. The bianisotropy model suggests that materials with planar anisotropy outperform those with uniaxial anisotropy in terms of high-frequency soft magnetic properties.23 According to our previous work, the magnetocrystalline anisotropy of Y2Fe14B compounds can be modified by adjusting the Sm content, making them suitable as soft magnetic materials.24 Despite this, as magnetic alloys, rare-earth transition metal intermetallic compounds exhibit significant power loss in the megahertz range, which limits their application.
To reduce power loss in soft magnetic materials, metal-based soft magnetic composites (SMCs) have been widely studied.25–30 These composites (SMCs) consist of soft magnetic particles and insulating media, where the soft magnetic particles are mainly Fe-based particles or ferrous alloys particles with micrometer-sized dimensions, and the insulating mediums are categorized into organic (e.g., epoxy resin) and inorganic media (e.g., SiO2, Al2O3, and MgO).31–38 Although a high concentration of the insulating medium can effectively reduce power loss, it also significantly decreases magnetic properties. According to previous works, the operating frequency in the megahertz range of soft magnetic composites results from nature resonance modulated by the eddy current effect, and the operating frequency of Fe4N is higher than Fe, where Fe4N is prepared from Fe by nitriding,28,39 this suggests that nitriding could potentially suppress the eddy current effect. The structures and properties of rare-earth transition metal intermetallic compounds can be modified by interstitial elements such as carbon (C), nitrogen (N), and hydrogen (H),40–46 suggesting interstitial solid solution of rare-earth transition metal intermetallic compounds are promising candidates for high-frequency soft magnetic materials.
To explore new methods for enhancing the operating frequency and reducing power loss in rare-earth transition metal intermetallic compounds, we systematically study the structure, magnetic properties, and power loss of (Y1−xSmx)2Fe14BNy compounds. Compared with (Y0.75Sm0.15)2Fe14B compounds, the operating frequency increased from to as well as the power loss decreased from to . Loss separation results indicate that the eddy loss was significantly reduced from to after nitriding, which demonstrates that nitriding is an effective method for reducing power loss in rare-earth transition metal intermetallic compounds. These results indicate nitrided rare-earth transition metal intermetallic compounds are promising candidates for high-frequency, low power loss soft magnetic materials.
II. EXPERIMENT
Alloy ingots of (Y1−xSmx)2Fe14B compounds with x = 0.00, 0.15, 0.30, 0.45, 0.60, 0.75, 0.90, and 1.00 were prepared via vacuum induction melting in a purified argon atmosphere. The purity of the Y, Sm, Fe, and B–Fe was 99.9% or higher. All alloy ingots were subsequently vacuum annealed at 1000 °C for 12 h to ensure homogeneity. Then, ingots were pulverized and heated in an atmosphere of purified N2 gas at 400 °C for 1 h. To obtain the complex relative permeability and power losses, the powders were coated by the 10 vol. % epoxy resins separately. Under 900 MPa, the insulated particle samples were pressed into rings with inner and outer diameters of 7 and 13 mm, respectively. In order to measure the conductivity, the insulated particle samples were pressed into disks with diameter of 10 mm under .
The x-ray powder diffraction (XRD) technique with Cu-Kα radiation (λ = 1.5418 Å) was used to identify the phases and the crystal structures of (Y1−xSmx)2Fe14BNy compounds. The Rietveld refinement technique was applied to (Y1−xSmx)2Fe14BNy compounds for crystal structure refinement by utilizing the GSAS-II software.47 The scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) were applied to characterize the morphology and the elemental distribution of the particles. The vibrating sample magnetometer (VSM) was used to measure static magnetic properties at room temperature (RT). The complex relative permeability was evaluated by the inductance (L)–capacitance (C)–resistance (R) method (LCR method). To further understand the effect of interstitial element N on high-frequency magnetic properties, the power loss was measured by B–H curve analyzer, and conductivity was measured by double testing digital four-probe tester.
III. RESULTS AND DISCUSSIONS
A. Phase and crystal structure
As shown in Fig. 1, the x-ray diffraction patterns of (Y1−xSmx)2Fe14BNy powders at room temperature were analyzed using Rietveld refinement with the tetragonal structure (space group P42/mnm, ICSD: 98-007-4384). A minor second phase was identified as cubic Fe (space group Im–3m, ICSD: 98-063-1734). The (120), (140), and (011) peaks are typical peaks of the tetragonal Y2Fe14BN0.3 phase and the cubic Fe phase, respectively. The mass fraction of the Y2Fe14BN0.3 phase can be confirmed by XRD refinements, which is greater than 82% with and . The mass fractions of Fe are summarized in Table I.
Refined room temperature x-ray diffraction patterns of (Y1−xSmx)2Fe14BNy compounds.
Refined room temperature x-ray diffraction patterns of (Y1−xSmx)2Fe14BNy compounds.
The mass fractions of Fe in (Y1−xSmx)2Fe14BNy compounds.
X . | 0.00 . | 0.15 . | 0.30 . | 0.45 . | 0.60 . | 0.75 . | 0.90 . | 1.00 . |
---|---|---|---|---|---|---|---|---|
Weight percentage | 8.3% | 18.0% | 8.7% | 8.6% | 11.0% | 3.7% | 7.0% | 2.9% |
X . | 0.00 . | 0.15 . | 0.30 . | 0.45 . | 0.60 . | 0.75 . | 0.90 . | 1.00 . |
---|---|---|---|---|---|---|---|---|
Weight percentage | 8.3% | 18.0% | 8.7% | 8.6% | 11.0% | 3.7% | 7.0% | 2.9% |
Figure 2 shows the crystal structure and atomic distribution obtained from XRD refinements. Figure 2(a) illustrates the atomic distribution in the unit cell of (Y1−xSmx)2Fe14BNy compounds, where N atoms have occupied 4f interstitial sites in the crystal structure. Figures 2(b) and 2(c) display the typical diffraction peaks of (Y1−xSmx)2Fe14B and (Y1−xSmx)2Fe14BNy compounds with x = 0.45 and 1. After nitriding, the diffraction peaks turn to the left, indicating lattice expansion. Figure 2(c) illustrates the lattice parameters a and c. The lattice parameters a and c of (Y1−xSmx)2Fe14BNy compounds are larger than those of (Y1−xSmx)2Fe14B with the same Sm content x, which demonstrates that N atoms have entered the unit cell.
The crystal structure and atomic distribution of (Y1−xSmx)2Fe14BNy compounds. (a) Atomic distribution in the unit cell of (Y1−xSmx)2Fe14BNy compounds. (b) Typical diffraction peaks of R2Fe14B and R2Fe14BNy phases with and . (c) Sm concentration dependence of lattice parameters a and c.
The crystal structure and atomic distribution of (Y1−xSmx)2Fe14BNy compounds. (a) Atomic distribution in the unit cell of (Y1−xSmx)2Fe14BNy compounds. (b) Typical diffraction peaks of R2Fe14B and R2Fe14BNy phases with and . (c) Sm concentration dependence of lattice parameters a and c.
B. Morphology and elements distribution
The SEM images and energy dispersive x-ray spectroscopy results are shown in Figs. 3 and 4. Figures 3(a) and 3(b) display the morphology and particle size distribution of (Y1−xSmx)2Fe14BNy powders, which exhibit a loose and irregular distribution with average particle size of 6–11 μm. The elemental analysis results by EDS for (Y0.75Sm0.15)2Fe14BNy particles are shown in Figs. 4(b)–4(f), corresponding to the area shown in Fig. 4(a). The distribution of N coincides with that of Y, Sm, Fe, and B, further confirming that N atoms have entered the (Y1−xSmx)2Fe14B unit cell.
The morphology and particle size distribution of (Y1−xSmx)2Fe14BNy powders. (a) The SEM images of (Y1−xSmx)2Fe14BNy particles. (b) The particle size distribution of (Y1−xSmx)2Fe14BNy powders.
The morphology and particle size distribution of (Y1−xSmx)2Fe14BNy powders. (a) The SEM images of (Y1−xSmx)2Fe14BNy particles. (b) The particle size distribution of (Y1−xSmx)2Fe14BNy powders.
The elements distribution of (Y1−xSmx)2Fe14BNy powder particles. (b)–(f) The element distribution of Y, Sm, Fe, B, and N obtained from the area of (a).
The elements distribution of (Y1−xSmx)2Fe14BNy powder particles. (b)–(f) The element distribution of Y, Sm, Fe, B, and N obtained from the area of (a).
C. Static magnetic properties
The static magnetic properties of (Y1−xSmx)2Fe14BNy compounds were obtained from the hysteresis loops of compounds. The remanence , coercivity , saturation magnetization , and the Curie temperature are summarized in Table II. The variation in the static magnetic properties of (Y1−xSmx)2Fe14BNy compounds with x follows the same trend as that observed in (Y1−xSmx)2Fe14B compounds. As the Sm content increases, the saturation magnetization reaches a maximum at x = 0.15 and then decreases, whereas the coercivity and remanence exhibit the opposite trend, reaching a minimum at x = 0.15, then increasing. High saturation magnetization , low remanence , and coercivity indicate that (Y1−xSmx)2Fe14BNy compounds exhibit soft magnetic characteristics. The Curie temperatures increase with increasing Sm content x and remain above 300 °C.
The static magnetic properties (remanence Mr, coercivity Hc, saturation magnetization Ms, and Curie temperature Tc) of (Y1−xSmx)2Fe14BNy compounds.
X . | Mr . | Hc (A m−1) . | Ms . | Tc (°C) . |
---|---|---|---|---|
0.00 | 6.2 | 7265.4 | 138.9 | 308.0 |
0.15 | 5.2 | 3779.9 | 146.3 | 308.1 |
0.30 | 5.6 | 5005.4 | 136.4 | 318.1 |
0.45 | 8.8 | 7018.7 | 136.2 | 328.1 |
0.60 | 10.1 | 8284.0 | 132.9 | 338.0 |
0.75 | 8.7 | 8204.4 | 129.4 | 348.1 |
0.90 | 13.4 | 13695.3 | 132.7 | 358.1 |
1.00 | 12.8 | 14984.4 | 107.7 | 368.0 |
X . | Mr . | Hc (A m−1) . | Ms . | Tc (°C) . |
---|---|---|---|---|
0.00 | 6.2 | 7265.4 | 138.9 | 308.0 |
0.15 | 5.2 | 3779.9 | 146.3 | 308.1 |
0.30 | 5.6 | 5005.4 | 136.4 | 318.1 |
0.45 | 8.8 | 7018.7 | 136.2 | 328.1 |
0.60 | 10.1 | 8284.0 | 132.9 | 338.0 |
0.75 | 8.7 | 8204.4 | 129.4 | 348.1 |
0.90 | 13.4 | 13695.3 | 132.7 | 358.1 |
1.00 | 12.8 | 14984.4 | 107.7 | 368.0 |
D. Dynamic magnetic properties
The dynamic magnetic properties are key properties of soft magnetic materials. Figure 5 shows the frequency dependences of the complex relative permeability for (Y1−xSmx)2Fe14BNy compounds. Compared with (Y1−xSmx)2Fe14B compounds from our previous work,24 the real part of relative permeability decreases slightly, while the operating frequency increases and the peak value of the imaginary part decreases dramatically. For the compound with , the real part of relative permeability decreases from 9.8 to 8.7 at 1 MHz, which is superior to other nitrided rare-earth transition metal intermetallic compounds and comparable to Co2Z-type ferrites.48–55 However, the imaginary part of relative permeability decreases from 6.1 to 1.6, and the operating frequency increases from 1.7 to 5.5 MHz. These results indicate that nitriding significantly enhances the operating frequency of rare-earth soft magnetic materials.
Frequency dependences of the complex relative permeability for (Y1−xSmx)2Fe14BNy compounds. (a) Real part of the complex relative permeability. (b) Imaginary part of the complex relative permeability.
Frequency dependences of the complex relative permeability for (Y1−xSmx)2Fe14BNy compounds. (a) Real part of the complex relative permeability. (b) Imaginary part of the complex relative permeability.
E. The power loss and loss separation
In order to confirm the reasons for the increase in operating frequency, the power loss results of (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy at 5 mT in 100–900 kHz are shown in Fig. 6. The power loss increases with frequency, but it is evident that the of (Y0.75Sm0.15)2Fe14BNy is significantly lower than that of (Y0.75Sm0.15)2Fe14B with values of and , respectively. The conductivity decreases about 43% by nitriding from 9380.9 to 5359.0 S/m, which indicates that the resistivity of (Y0.75Sm0.15)2Fe14B increases by nitriding. These results suggest that the interstitial element nitrogen can effectively reduce the power loss and increases resistivity in rare-earth transition metal intermetallic compounds.
The power loss for (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy composites. The inset is the conductivity of (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy composites.
The power loss for (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy composites. The inset is the conductivity of (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy composites.
Simulated parameters for loss separation of (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy compounds.
. | Physt . | Peddy . | Pexc . | |
---|---|---|---|---|
Chyst . | α . | Ceddy . | Cexc . | |
(Y0.75Sm0.15)2Fe14B | 38.33 | 2.22 | 6.90 × 10−5 | 5.60 × 10−19 |
(Y0.75Sm0.15)2Fe14BNy | 49.01 | 2.44 | 2.70 × 10−5 | 1.00 × 10−20 |
. | Physt . | Peddy . | Pexc . | |
---|---|---|---|---|
Chyst . | α . | Ceddy . | Cexc . | |
(Y0.75Sm0.15)2Fe14B | 38.33 | 2.22 | 6.90 × 10−5 | 5.60 × 10−19 |
(Y0.75Sm0.15)2Fe14BNy | 49.01 | 2.44 | 2.70 × 10−5 | 1.00 × 10−20 |
The results of loss separation are shown in Fig. 7. Based on these results, in the low frequency range, the primary loss mechanism in both (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy compounds is , whereas in high frequency, the primary loss mechanism is , with the accounting for 84.6% and 82.5% of the power loss at 900 kHz, respectively. The changes in Physt and Pexc are similar before and after nitrogenation. Notably, the of (Y0.75Sm0.15)2Fe14B decreases dramatically from to after nitriding at 900 kHz, which indicates that the resistivity of (Y0.75Sm0.15)2Fe14B increases by nitriding and leads to a reduction in . The proportions of the three types of losses are shown in Table IV. These results provide an effective approach for reducing power loss and enhancing the operating frequency of rare-earth soft magnetic materials.
The loss separation for (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy compounds. (a) (Y0.75Sm0.15)2Fe14B and (b) (Y0.75Sm0.15)2Fe14BNy.
The loss separation for (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy compounds. (a) (Y0.75Sm0.15)2Fe14B and (b) (Y0.75Sm0.15)2Fe14BNy.
The proportion of hysteresis loss, Eddy current loss, and excess loss for (Y0.75Sm0.15)2Fe14B and (Y0.75Sm0.15)2Fe14BNy compounds at 100–900 kHz.
(a) (Y0.75Sm0.15)2Fe14B . | 10 0 kHz . | 200 kHz . | 300 kHz . | 400 kHz . | 500 kHz . | 600 kHz . | 700 kHz . | 800 kHz . | 900 kHz . |
---|---|---|---|---|---|---|---|---|---|
Hysteresis loss | 61.1% | 43.8% | 34.8% | 28.1% | 24.1% | 20.9% | 18.8% | 16.9% | 15.3% |
Eddy current loss | 37.5% | 53.8% | 64.1% | 69.1% | 73.9% | 77.2% | 80.6% | 83.0% | 84.6% |
Excess loss | 1.4% | 2.4% | 1.1% | 2.8% | 2.0% | 1.9% | 0.6% | 0.1% | 0.1% |
(a) (Y0.75Sm0.15)2Fe14B . | 10 0 kHz . | 200 kHz . | 300 kHz . | 400 kHz . | 500 kHz . | 600 kHz . | 700 kHz . | 800 kHz . | 900 kHz . |
---|---|---|---|---|---|---|---|---|---|
Hysteresis loss | 61.1% | 43.8% | 34.8% | 28.1% | 24.1% | 20.9% | 18.8% | 16.9% | 15.3% |
Eddy current loss | 37.5% | 53.8% | 64.1% | 69.1% | 73.9% | 77.2% | 80.6% | 83.0% | 84.6% |
Excess loss | 1.4% | 2.4% | 1.1% | 2.8% | 2.0% | 1.9% | 0.6% | 0.1% | 0.1% |
(b) (Y0.75Sm0.15)2Fe14BNy . | |||||||||
---|---|---|---|---|---|---|---|---|---|
Hysteresis loss | 58.5% | 43.5% | 32.7% | 29.1% | 24.1% | 21.4% | 19.4% | 17.5% | 16.2% |
Eddy current loss | 33.1% | 49.4% | 55.6% | 66.0% | 68.3% | 72.9% | 76.8% | 79.3% | 82.5% |
Excess loss | 8.4% | 7.1% | 11.7% | 4.9% | 7.6% | 5.7% | 1.3% | 3.2% | 1.3% |
(b) (Y0.75Sm0.15)2Fe14BNy . | |||||||||
---|---|---|---|---|---|---|---|---|---|
Hysteresis loss | 58.5% | 43.5% | 32.7% | 29.1% | 24.1% | 21.4% | 19.4% | 17.5% | 16.2% |
Eddy current loss | 33.1% | 49.4% | 55.6% | 66.0% | 68.3% | 72.9% | 76.8% | 79.3% | 82.5% |
Excess loss | 8.4% | 7.1% | 11.7% | 4.9% | 7.6% | 5.7% | 1.3% | 3.2% | 1.3% |
IV. CONCLUSION
In conclusion, N atoms can be incorporated into (Y1−xSmx)2Fe14B unit cell to synthesize (Y1−xSmx)2Fe14BNy compounds, leading to increase in operating frequency and reduction in power loss. The static magnetic properties indicate that (Y1−xSmx)2Fe14BNy compounds exhibit soft magnetic characteristics with the Curie temperature exceeding 300.0 °C. The dynamic magnetic properties measurements show the operating frequency increases from 1.7 to 5.5 MHz, while the imaginary part of relative permeability decreases from 6.1 to 1.6 by nitriding. The power loss decreases from to , and the conductivity decreases about 43% by nitriding, from 9380.9 to 5359.0 S/m. Loss separation reveals that eddy current loss plays a dominant role in power loss at high-frequency range and is significantly suppressed by nitriding. These findings offer an effective approach to developing novel high-frequency, low power loss rare-earth soft magnetic materials.
ACKNOWLEDGMENTS
This work was supported by the National Key R & D Program of China (No. 2021YFB3501300), the NSFC (Grant Nos. 91963201 and 12174163), and the 111 Project under Grant No. B20063.
AUTHOR DECLARATIONS
Conflict of Interest
The authors have no conflicts to disclose.
Author Contributions
Chao Meng: Data curation (lead); Formal analysis (lead); Investigation (lead); Methodology (lead); Writing – original draft (lead); Writing – review & editing (equal). Zenan Zhang: Investigation (equal); Methodology (equal); Writing – review & editing (equal). Zhaochen Liu: Investigation (equal); Writing – review & editing (equal). Xiaowei Jin: Writing – review & editing (equal). Zhenlin Jia: Writing – review & editing (equal). Hao Feng: Investigation (equal); Writing – review & editing (equal). Desheng Xue: Conceptualization (lead); Funding acquisition (lead); Writing – review & editing (lead).
DATA AVAILABILITY
The data that support the findings of this study are available from the corresponding author upon reasonable request.