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Magnetic properties of zero-magnetostrictive nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with high magnetic induction
Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
Magnetic properties of zero-magnetostrictive nanocrystalline Fe}Zr}Nb}B soft magnetic alloys with high magnetic induction A. Makino , T. Bitoh *, A. Kojima, A. Inoue, T. Masumoto Department of Machine Intelligence and System Engineering, Akita Prefectural University, Honjo 015-0055, Japan Central Research Laboratory, Alps Electric Co., Ltd., Nagaoka 940-8572, Japan Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan The Research Institute of Electrical and Magnetic Materials, Sendai 982-0807, Japan
Abstract The soft magnetic properties of the nanocrystalline Fe}Zr}Nb}B alloys have been investigated. The best soft magnetic properties have been obtained for the Fe Zr Nb B alloy. The alloy shows a high permeability of 60,000 at 1 kHz, a high magnetic induction of 1.64 T and zero magnetostriction, simultaneously. The alloy also exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is extremely lower than that of Fe}Si}B amorphous. The nanocrystalline Fe}Zr}Nb}B alloy is therefore suitable for a core material for pole transformers. 2000 Elsevier Science B.V. All rights reserved. Keywords: Nanocrystalline alloy; Melt-spun ribbon; Crystallization; Soft magnetic properties; High permeability; High saturation magnetic induction; Low core loss; Zero magnetostriction
1. Introduction Recently, a great interest in environmental protection has been arisen. Energy saving is considered as one of important problems of the world. As a solution for the energy saving, replacement of conventional Si-steels used as a core material for pole transformers by Fe-based amorphous alloys with low core losses is now in progress. In addition, development of new soft magnetic materials exhibiting lower core losses than those of the Fe-based amorphous alloys is expected. In the last decade, some nanocrystalline soft magnetic alloys consisting of BCC nanoscale crystalline phase have been obtained by crystallizing melt-spun amorphous ribbons. In 1988, the crystallization of Fe}Si}B amorphous alloys containing Nb and Cu causes the formation of a nanoscale BCC Fe}Si structure and the
* Corresponding author. Fax: #81-184-27-2211. E-mail address: teruo}[email protected] (T. Bitoh).
BCC alloys exhibit good soft magnetic properties of 1.2}1.4 T for saturation magnetic induction (B ) and high permeability (l ) [1]. Although the good soft magnetic properties are obtained for the nanoscale BCC Fe Si B Nb Cu , relatively low Fe concentration led to the limitation of B less than 1.4 T and hence the development of a new soft magnetic alloy with high B above 1.5 T has strongly been desired because the high B is necessary to use as a core material for the pole transformers. We tried to synthesize a nanocrystalline soft magnetic material with high B , and have developed nanocrystal line Fe}M}B (M"Zr, Hf or Nb) alloys with high B more than 1.5 T as well as good soft magnetic proper ties [2]. The formation of amorphous phases in Femetalloid systems such as Fe}Si}B and Fe}P}C alloys by the melt-spinning method usually occurs in a range of 70}84 at% Fe [3]. On the other hand, amorphous phases have been obtained in the range of 88}91 at% Fe for Fe-transition metal systems such as Fe}Zr [4] and Fe}Hf [5] alloys. In addition, it has been reported that the addition of a small amount of B to Fe}Zr and Fe}Hf
0304-8853/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 1 3 6 - 0
A. Makino et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
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Table 1 Mean grain size (D), saturation induction (B ), permeability (k ), coercivity (H ), magnetostriction (j ) and core loss (W) of nanocrystal line ternary Fe}M}B alloys and Fe}Si}B amorphous alloy
Fe Zr B Fe Nb B Fe B Si (amor.)
D (nm)
B (T)
k
H (A/m)
j (10\)
= (W/kg)
13 11 *
1.70 1.52 1.56
30,000 51,000 10,000
5.8 4.8 3.5
!1.1 0.2 27
0.21 0.14 0.28
1 kHz, 0.4 A/m 50 Hz, 1.4 T
alloys extends the glass formation range [6,7]. The high volume fraction of the a-Fe phase has been obtained by crystallizing the amorphous Fe}M}B alloys with the high Fe concentration. Table 1 shows the properties of the typical ternary Fe}M}B alloys. It should be noted that the ternary Fe}M}B alloys exhibit small but non-zero magnetostriction (j ). It is expected that the soft magnetic properties of the Fe}M}B alloys can be improved further by achieving zero-j . In this paper, we report the soft magnetic properties of the Fe}Zr}Nb}B alloys, which are mixed Fe}Zr}B alloy with negative j and Fe}Nb}B alloy with positive j . 2. Experimental procedure Alloy ingots were prepared by arc or induction melting in an Ar atmosphere. A single-roller melt-spinning method in an Ar atmosphere was used to produce the rapidly solidi"ed ribbons with 15 mm in width and 20}25 lm in thickness. The as-quenched ribbons were mechanically punched to be used as samples. Annealing treatment of the samples was carried out by treating the samples for 300 s at various temperatures in a vacuum; the heating rate was 3 K/s. The mean grain size of the a-Fe phase (D) was evaluated by using Scherrer's equation from the half-width of (1 1 0) re#ection peak. The saturation magnetic induction (B ) under an applied "eld of 800 kA/m was measured by a vibrating sample magnetometer (VSM) using diskshaped samples with 6 mm in diameter. Measurements of the permeability (k ) and the core loss (W) were per formed with ring-shaped samples with 6 mm in inner diameter and 10 mm in outer diameter. The permeability was measured by a vector impedance analyzer at 1 kHz under a "eld of 0.4 A/m. An AC B!H analyzer operated under sinusoidal input voltage was used to measure W. The saturation magnetostriction (j ) under a "eld of 80 kA/m was evaluated by a strain gage technique with disk-shaped samples with 10 mm in diameter.
3. Results and discussion In the nanocrystalline Fe}Zr}B and Fe}Nb}B alloys, the compositional range where k shows a maximum does not strictly coincide with zero-j line as mentioned above [8]. The best soft magnetic properties are obtained around the compositions of Fe Zr B and Fe Nb B . Since j changes from negative to positive with increasing B content for the alloys, j of the Fe Zr B alloy is nega tive whereas that of the Fe Nb B alloys is positive. First, Zr, Nb and B concentrations were investigated by choosing the Fe Zr B and Fe Nb B alloys as basic constituents and mixing them in various ratios. Fig. 1 shows the compositional dependence of (a) B , (b) k , (c) D and (d) j of the (Fe Zr B ) (Fe Nb B ) alloys \V V as a function of x. The saturation induction, D and j of the (Fe Zr B ) (Fe Nb B ) alloys show inter \V V mediate values between those of the Fe Zr B and the Fe Nb B alloys. However, k values of the (Fe Zr B ) (Fe Nb B ) alloys are less than those \V V of the Fe Zr B and the Fe Nb B alloys. It is noted that k shows a minimum around x"0.8 where the alloy exhibits zero-j . This result implies that the soft magnetic properties of the Fe}Zr}Nb}B alloy are strongly a!ected by other factors. Next, we studied the e!ect of Zr#Nb amount on the soft magnetic properties. The best soft magnetic properties have been obtained at Zr#Nb"6 at%. Fig. 2 shows the pseudo-ternary diagram of k (solid lines), B (broken lines), j (dotted lines) for Fe}(Zr, Nb)}B alloys crystallized under optimum conditions, where the Zr # Nb amount was constant at 6 at%. The small grain size of 10}11 nm has been obtained in a compositional range of 0}3 at% Zr and 6}9 at% B. The permeability reaches the maximum value of 60,000 for the Fe Zr Nb B alloy, which shows zero-j . It should be noted that the best soft magnetic properties have been obtained around Zr : Nb"2 : 4 when Zr#Nb"6 at %. As shown in Fig. 1, k shows the minimum around Zr : Nb"2 : 4 when Zr#Nb"7 at%, whereas zero-j has been obtained.
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Fig. 2. Pseudo-ternary diagram of permeability (k ), saturation induction (B ) and magnetostriction (j ) for nanocrystalline Fe}(Zr, Nb) B alloys after annealing at the optimum conditions.
Fig. 1. Compositional dependence of (a) saturation induction (B ), (b) permeability (k ), (c) mean grain size (D) and (d) magnetostriction (j ) for nanocrystalline (Fe Zr B ) (Fe Nb B ) alloys after annealing at the op \V V timum conditions.
Fig. 3 shows the annealing temperature (¹ ) dependence of (a) B , (b) k , (c) Curie temperature (¹ ) of amorphous phase, (d) D and (e) j of the Fe Zr Nb B alloy. The date for Fe Zr B and Fe Nb B are also shown. The Curie temperature of the amorphous phase was evaluated from an in#ection point of B versus temperature curves. The nanocrystal line Fe}M}B alloys consist of the nanoscale a-Fe grains embedded in a residual amorphous minority matrix. The strong intergranular coupling is important to achieve the good soft magnetic properties [9]. The intergranular coupling in the Fe}M}B alloys is mediated by the residual amorphous phase. When ¹ of the residual amorph ous phase is low, it cannot fully mediate the intergranular interaction owing to the thermal #uctuation of the spins
in the amorphous phase. Therefore, high ¹ of the resid ual amorphous phase is necessary to obtain the good soft magnetic properties. The amorphous Fe-rich Fe}M}B alloys exhibit low ¹ due to an Inver e!ect [10]. The Curie temperature of the residual amorphous phase increases with increasing ¹ owing to the enrichment of Zr, Nb and B in the residual amorphous phase by the di!usion of the elements out of the a-Fe grains [9]. As shown in Fig. 3(c), the Fe Zr Nb B alloy exhibits higher ¹ of the residual amorphous phase than that of the Fe Zr B and the Fe Nb B alloys. This is a reason why the Fe Zr Nb B alloy shows better soft mag netic properties. The saturation induction of the Fe}M}B alloys increases rapidly with increasing ¹ in the range from 748 to 823 K, where the structure changes from the amorphous phase with low ¹ to a-Fe#the residual amorphous phase. The permeability of the alloys increase with increasing ¹ and reaches the maximum value of 30,000}60,000, where small D and nearly zero-j are achieved. It should be noted that the increase of k with the structural change is steeper than that of the Fe Zr B and the Fe Nb B alloys. The low-frequency soft magnetic properties of the Fe Zr Nb B alloy have been studied to examine an application potential as a core material for the pole transformers. Fig. 4 shows the core loss at 50 Hz of the nanocrystalline Fe Zr Nb B alloy as a function of maximum induction (B ), along with the data for the
nanocrystalline Fe Zr B , Fe Nb B alloys and
A. Makino et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
291
Fig. 4. Core loss (=) at 50 Hz as a function of maximum induction (B ) for nanocrystalline Fe Zr B , Fe Nb B ,
Fe Zr Nb B alloys and amorphous Fe Si B alloy.
4. Conclusion
Fig. 3. Changes in (a) saturation induction (B ), (b) permeability (k ), (c) Curie temperature (¹ ) of amorphous phase, (d) mean grain size (D) and (e) magnetostriction (j ) as a function of annealing temperature (¹ ) for nanocrystalline Fe Zr B , Fe Nb B , Fe Zr Nb B alloys.
a commercial amorphous Fe Si B alloy. The Fe Zr Nb B alloy exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is 1/2}2/3 that of the Fe}M}B ternary alloys and is extremely lower than that of the amorphous Fe Si B alloy. Furthermore, it was con"rmed that the Fe Zr Nb B alloy also has a good thermal stability of the magnetic properties. The Fe Zr Nb B alloy is therefore suitable for a core material for the pole transformers. The present work reveals that the soft magnetic properties of the Fe}Zr}Nb}B alloys are strongly a!ected by the Zr#Nb amount and the Zr/Nb ratio. However, the in#uence of mixing Zr and Nb on the microstructure and the magnetic properties is still unclear. Further investigations are required.
The soft magnetic properties of the Fe}Zr}Nb}B alloys have been investigated. It is revealed that the soft magnetic properties of the alloys are strongly a!ected by the Zr#Nb amount and the Zr/Nb ratio. The best soft magnetic properties have been obtained at Zr#Nb" 6 at%. The Fe Zr Nb B alloy shows the high k of 60,000 at 1 kHz, the high B of 1.64 T and zero-k , simul taneously. The alloy also exhibits the very low core loss of 0.09 W/kg at 1.4 T and 50 Hz and the good thermal stability of the magnetic properties. It can be concluded that the nanocrystalline Fe Zr Nb B alloy with high B is suitable for a core material for the pole trans formers. Acknowledgements This work was partly supported by a grant-in-aid from the New Energy and Industrial Technology Development Organization (NEDO). References [1] Y. Yoshizawa, S. Oguma, K. Yamauchi, J. Appl. Phys. 64 (1988) 6044.
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[2] A. Makino, K. Suzuki, A. Inoue, Y. Hirotsu, T. Masumoto, J. Magn. Magn. Mater. 133 (1994) 329. [3] T. Masumoto et al. (Eds.), Materials Science of Amorphous Metals, Ohmu, Tokyo, 1982, p. 281. [4] M. Nose, T. Masumoto, Sci. Rep. RITU A 28 (1980) 232. [5] A. Inoue, K. Kobayashi, T. Masumoto, in: C. Hargitai et al. (Eds.), Proceedings of Conference on Metallic Glasses, Science and Technology, Vol. II, Cent. Res. Inst. Phys., Budapest, 1980, p. 217.
[6] A. Inoue, K. Kobayashi, M. Nose, T. Masumoto, J. Phys. C 8}41 (1980) 31. [7] S. Ohnuma, M. Nose, K. Shirakawa, T. Masumoto, Sci. Rep. RITU A 29 (1981) 254. [8] A. Makino, A. Inoue, T. Masumoto, Mater. Trans. JIM 36 (1995) 924. [9] G. Herzer, IEEE Trans. Magn. 25 (1989) 3327. [10] K. Shirakawa, S. Ohmuma, M. Nose, T. Masumoto, IEEE Trans. Magn. MAG-16 (1980) 910.
Magnetic properties of zero-magnetostrictive nanocrystalline Fe}Zr}Nb}B soft magnetic alloys with high magnetic induction A. Makino , T. Bitoh *, A. Kojima, A. Inoue, T. Masumoto Department of Machine Intelligence and System Engineering, Akita Prefectural University, Honjo 015-0055, Japan Central Research Laboratory, Alps Electric Co., Ltd., Nagaoka 940-8572, Japan Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan The Research Institute of Electrical and Magnetic Materials, Sendai 982-0807, Japan
Abstract The soft magnetic properties of the nanocrystalline Fe}Zr}Nb}B alloys have been investigated. The best soft magnetic properties have been obtained for the Fe Zr Nb B alloy. The alloy shows a high permeability of 60,000 at 1 kHz, a high magnetic induction of 1.64 T and zero magnetostriction, simultaneously. The alloy also exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is extremely lower than that of Fe}Si}B amorphous. The nanocrystalline Fe}Zr}Nb}B alloy is therefore suitable for a core material for pole transformers. 2000 Elsevier Science B.V. All rights reserved. Keywords: Nanocrystalline alloy; Melt-spun ribbon; Crystallization; Soft magnetic properties; High permeability; High saturation magnetic induction; Low core loss; Zero magnetostriction
1. Introduction Recently, a great interest in environmental protection has been arisen. Energy saving is considered as one of important problems of the world. As a solution for the energy saving, replacement of conventional Si-steels used as a core material for pole transformers by Fe-based amorphous alloys with low core losses is now in progress. In addition, development of new soft magnetic materials exhibiting lower core losses than those of the Fe-based amorphous alloys is expected. In the last decade, some nanocrystalline soft magnetic alloys consisting of BCC nanoscale crystalline phase have been obtained by crystallizing melt-spun amorphous ribbons. In 1988, the crystallization of Fe}Si}B amorphous alloys containing Nb and Cu causes the formation of a nanoscale BCC Fe}Si structure and the
* Corresponding author. Fax: #81-184-27-2211. E-mail address: teruo}[email protected] (T. Bitoh).
BCC alloys exhibit good soft magnetic properties of 1.2}1.4 T for saturation magnetic induction (B ) and high permeability (l ) [1]. Although the good soft magnetic properties are obtained for the nanoscale BCC Fe Si B Nb Cu , relatively low Fe concentration led to the limitation of B less than 1.4 T and hence the development of a new soft magnetic alloy with high B above 1.5 T has strongly been desired because the high B is necessary to use as a core material for the pole transformers. We tried to synthesize a nanocrystalline soft magnetic material with high B , and have developed nanocrystal line Fe}M}B (M"Zr, Hf or Nb) alloys with high B more than 1.5 T as well as good soft magnetic proper ties [2]. The formation of amorphous phases in Femetalloid systems such as Fe}Si}B and Fe}P}C alloys by the melt-spinning method usually occurs in a range of 70}84 at% Fe [3]. On the other hand, amorphous phases have been obtained in the range of 88}91 at% Fe for Fe-transition metal systems such as Fe}Zr [4] and Fe}Hf [5] alloys. In addition, it has been reported that the addition of a small amount of B to Fe}Zr and Fe}Hf
0304-8853/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 1 3 6 - 0
A. Makino et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
289
Table 1 Mean grain size (D), saturation induction (B ), permeability (k ), coercivity (H ), magnetostriction (j ) and core loss (W) of nanocrystal line ternary Fe}M}B alloys and Fe}Si}B amorphous alloy
Fe Zr B Fe Nb B Fe B Si (amor.)
D (nm)
B (T)
k
H (A/m)
j (10\)
= (W/kg)
13 11 *
1.70 1.52 1.56
30,000 51,000 10,000
5.8 4.8 3.5
!1.1 0.2 27
0.21 0.14 0.28
1 kHz, 0.4 A/m 50 Hz, 1.4 T
alloys extends the glass formation range [6,7]. The high volume fraction of the a-Fe phase has been obtained by crystallizing the amorphous Fe}M}B alloys with the high Fe concentration. Table 1 shows the properties of the typical ternary Fe}M}B alloys. It should be noted that the ternary Fe}M}B alloys exhibit small but non-zero magnetostriction (j ). It is expected that the soft magnetic properties of the Fe}M}B alloys can be improved further by achieving zero-j . In this paper, we report the soft magnetic properties of the Fe}Zr}Nb}B alloys, which are mixed Fe}Zr}B alloy with negative j and Fe}Nb}B alloy with positive j . 2. Experimental procedure Alloy ingots were prepared by arc or induction melting in an Ar atmosphere. A single-roller melt-spinning method in an Ar atmosphere was used to produce the rapidly solidi"ed ribbons with 15 mm in width and 20}25 lm in thickness. The as-quenched ribbons were mechanically punched to be used as samples. Annealing treatment of the samples was carried out by treating the samples for 300 s at various temperatures in a vacuum; the heating rate was 3 K/s. The mean grain size of the a-Fe phase (D) was evaluated by using Scherrer's equation from the half-width of (1 1 0) re#ection peak. The saturation magnetic induction (B ) under an applied "eld of 800 kA/m was measured by a vibrating sample magnetometer (VSM) using diskshaped samples with 6 mm in diameter. Measurements of the permeability (k ) and the core loss (W) were per formed with ring-shaped samples with 6 mm in inner diameter and 10 mm in outer diameter. The permeability was measured by a vector impedance analyzer at 1 kHz under a "eld of 0.4 A/m. An AC B!H analyzer operated under sinusoidal input voltage was used to measure W. The saturation magnetostriction (j ) under a "eld of 80 kA/m was evaluated by a strain gage technique with disk-shaped samples with 10 mm in diameter.
3. Results and discussion In the nanocrystalline Fe}Zr}B and Fe}Nb}B alloys, the compositional range where k shows a maximum does not strictly coincide with zero-j line as mentioned above [8]. The best soft magnetic properties are obtained around the compositions of Fe Zr B and Fe Nb B . Since j changes from negative to positive with increasing B content for the alloys, j of the Fe Zr B alloy is nega tive whereas that of the Fe Nb B alloys is positive. First, Zr, Nb and B concentrations were investigated by choosing the Fe Zr B and Fe Nb B alloys as basic constituents and mixing them in various ratios. Fig. 1 shows the compositional dependence of (a) B , (b) k , (c) D and (d) j of the (Fe Zr B ) (Fe Nb B ) alloys \V V as a function of x. The saturation induction, D and j of the (Fe Zr B ) (Fe Nb B ) alloys show inter \V V mediate values between those of the Fe Zr B and the Fe Nb B alloys. However, k values of the (Fe Zr B ) (Fe Nb B ) alloys are less than those \V V of the Fe Zr B and the Fe Nb B alloys. It is noted that k shows a minimum around x"0.8 where the alloy exhibits zero-j . This result implies that the soft magnetic properties of the Fe}Zr}Nb}B alloy are strongly a!ected by other factors. Next, we studied the e!ect of Zr#Nb amount on the soft magnetic properties. The best soft magnetic properties have been obtained at Zr#Nb"6 at%. Fig. 2 shows the pseudo-ternary diagram of k (solid lines), B (broken lines), j (dotted lines) for Fe}(Zr, Nb)}B alloys crystallized under optimum conditions, where the Zr # Nb amount was constant at 6 at%. The small grain size of 10}11 nm has been obtained in a compositional range of 0}3 at% Zr and 6}9 at% B. The permeability reaches the maximum value of 60,000 for the Fe Zr Nb B alloy, which shows zero-j . It should be noted that the best soft magnetic properties have been obtained around Zr : Nb"2 : 4 when Zr#Nb"6 at %. As shown in Fig. 1, k shows the minimum around Zr : Nb"2 : 4 when Zr#Nb"7 at%, whereas zero-j has been obtained.
290
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Fig. 2. Pseudo-ternary diagram of permeability (k ), saturation induction (B ) and magnetostriction (j ) for nanocrystalline Fe}(Zr, Nb) B alloys after annealing at the optimum conditions.
Fig. 1. Compositional dependence of (a) saturation induction (B ), (b) permeability (k ), (c) mean grain size (D) and (d) magnetostriction (j ) for nanocrystalline (Fe Zr B ) (Fe Nb B ) alloys after annealing at the op \V V timum conditions.
Fig. 3 shows the annealing temperature (¹ ) dependence of (a) B , (b) k , (c) Curie temperature (¹ ) of amorphous phase, (d) D and (e) j of the Fe Zr Nb B alloy. The date for Fe Zr B and Fe Nb B are also shown. The Curie temperature of the amorphous phase was evaluated from an in#ection point of B versus temperature curves. The nanocrystal line Fe}M}B alloys consist of the nanoscale a-Fe grains embedded in a residual amorphous minority matrix. The strong intergranular coupling is important to achieve the good soft magnetic properties [9]. The intergranular coupling in the Fe}M}B alloys is mediated by the residual amorphous phase. When ¹ of the residual amorph ous phase is low, it cannot fully mediate the intergranular interaction owing to the thermal #uctuation of the spins
in the amorphous phase. Therefore, high ¹ of the resid ual amorphous phase is necessary to obtain the good soft magnetic properties. The amorphous Fe-rich Fe}M}B alloys exhibit low ¹ due to an Inver e!ect [10]. The Curie temperature of the residual amorphous phase increases with increasing ¹ owing to the enrichment of Zr, Nb and B in the residual amorphous phase by the di!usion of the elements out of the a-Fe grains [9]. As shown in Fig. 3(c), the Fe Zr Nb B alloy exhibits higher ¹ of the residual amorphous phase than that of the Fe Zr B and the Fe Nb B alloys. This is a reason why the Fe Zr Nb B alloy shows better soft mag netic properties. The saturation induction of the Fe}M}B alloys increases rapidly with increasing ¹ in the range from 748 to 823 K, where the structure changes from the amorphous phase with low ¹ to a-Fe#the residual amorphous phase. The permeability of the alloys increase with increasing ¹ and reaches the maximum value of 30,000}60,000, where small D and nearly zero-j are achieved. It should be noted that the increase of k with the structural change is steeper than that of the Fe Zr B and the Fe Nb B alloys. The low-frequency soft magnetic properties of the Fe Zr Nb B alloy have been studied to examine an application potential as a core material for the pole transformers. Fig. 4 shows the core loss at 50 Hz of the nanocrystalline Fe Zr Nb B alloy as a function of maximum induction (B ), along with the data for the
nanocrystalline Fe Zr B , Fe Nb B alloys and
A. Makino et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
291
Fig. 4. Core loss (=) at 50 Hz as a function of maximum induction (B ) for nanocrystalline Fe Zr B , Fe Nb B ,
Fe Zr Nb B alloys and amorphous Fe Si B alloy.
4. Conclusion
Fig. 3. Changes in (a) saturation induction (B ), (b) permeability (k ), (c) Curie temperature (¹ ) of amorphous phase, (d) mean grain size (D) and (e) magnetostriction (j ) as a function of annealing temperature (¹ ) for nanocrystalline Fe Zr B , Fe Nb B , Fe Zr Nb B alloys.
a commercial amorphous Fe Si B alloy. The Fe Zr Nb B alloy exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is 1/2}2/3 that of the Fe}M}B ternary alloys and is extremely lower than that of the amorphous Fe Si B alloy. Furthermore, it was con"rmed that the Fe Zr Nb B alloy also has a good thermal stability of the magnetic properties. The Fe Zr Nb B alloy is therefore suitable for a core material for the pole transformers. The present work reveals that the soft magnetic properties of the Fe}Zr}Nb}B alloys are strongly a!ected by the Zr#Nb amount and the Zr/Nb ratio. However, the in#uence of mixing Zr and Nb on the microstructure and the magnetic properties is still unclear. Further investigations are required.
The soft magnetic properties of the Fe}Zr}Nb}B alloys have been investigated. It is revealed that the soft magnetic properties of the alloys are strongly a!ected by the Zr#Nb amount and the Zr/Nb ratio. The best soft magnetic properties have been obtained at Zr#Nb" 6 at%. The Fe Zr Nb B alloy shows the high k of 60,000 at 1 kHz, the high B of 1.64 T and zero-k , simul taneously. The alloy also exhibits the very low core loss of 0.09 W/kg at 1.4 T and 50 Hz and the good thermal stability of the magnetic properties. It can be concluded that the nanocrystalline Fe Zr Nb B alloy with high B is suitable for a core material for the pole trans formers. Acknowledgements This work was partly supported by a grant-in-aid from the New Energy and Industrial Technology Development Organization (NEDO). References [1] Y. Yoshizawa, S. Oguma, K. Yamauchi, J. Appl. Phys. 64 (1988) 6044.
292
A. Makino et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 288}292
[2] A. Makino, K. Suzuki, A. Inoue, Y. Hirotsu, T. Masumoto, J. Magn. Magn. Mater. 133 (1994) 329. [3] T. Masumoto et al. (Eds.), Materials Science of Amorphous Metals, Ohmu, Tokyo, 1982, p. 281. [4] M. Nose, T. Masumoto, Sci. Rep. RITU A 28 (1980) 232. [5] A. Inoue, K. Kobayashi, T. Masumoto, in: C. Hargitai et al. (Eds.), Proceedings of Conference on Metallic Glasses, Science and Technology, Vol. II, Cent. Res. Inst. Phys., Budapest, 1980, p. 217.
[6] A. Inoue, K. Kobayashi, M. Nose, T. Masumoto, J. Phys. C 8}41 (1980) 31. [7] S. Ohnuma, M. Nose, K. Shirakawa, T. Masumoto, Sci. Rep. RITU A 29 (1981) 254. [8] A. Makino, A. Inoue, T. Masumoto, Mater. Trans. JIM 36 (1995) 924. [9] G. Herzer, IEEE Trans. Magn. 25 (1989) 3327. [10] K. Shirakawa, S. Ohmuma, M. Nose, T. Masumoto, IEEE Trans. Magn. MAG-16 (1980) 910.