Characteristics of B2O3 and Fe Added Into BaFe12O19 Permanent Magnets Prepared At Different Milling Time and Sintering Temperature

  

Characteristics of B2O3 and Fe added into BaFe12O19 permanent magnets prepared at

different milling time and sintering temperature

Citation: View Table of Contents: Articles you may be interested in AIP Conference Proceedings 1801, 040007 (2017); 10.1063/1.4973096 AIP Advances 7, 055602 (2017); 10.1063/1.4978398 AIP Conference Proceedings 1711, 020002 (2016); 10.1063/1.4941611 AIP Conference Proceedings 1725, 020098 (2016); 10.1063/1.4945552 Journal of Applied Physics 117, 243904 (2015); 10.1063/1.4922867 Journal of Applied Physics 118, 203908 (2015); 10.1063/1.4936368

  Characteristics of B

2 O

  3 and Fe Added Into BaFe

  12 O

  19 Permanent Magnets Prepared At Different Milling Time

and Sintering Temperature

  Perdamean Sebayang 1)

  , Ayu Yuswita Sari 1)

  , Delovita Ginting 2)

  , Yola Allan

  2) , Nasruddin M. N.

  2) , Kerista Sebayang

  2)

  1 Research Center for Physics LIPI, Kawasan PUSPIPTEK, Serpong

• – Indonesia, 15314

  Corresponding author:

  and Sr.Fe

  

International Symposium on Frontier of Applied Physics (ISFAP) 2015

AIP Conf. Proc. 1711, 020004-1–020004-6; doi: 10.1063/1.4941613

© 2016 AIP Publishing LLC 978-0-7354-1358-0/$30.00

  3 have also been found to be useful as

  2 O

  3 , PbO and B

  2 O

  2 , Al

  Recently, many researchers focused on alloying element addition for improving the magnetic properties of the ferrite magnets. Various doping agent such as SiO

  ) have high saturation magnetizations (Ms) of 72 emu g-1 and at least 74 emu g-1 , respectively [Durmus, Z., Durmus, A., and Kavas, H., 2015, J Mater Sci 50, 1201-1213 (2015)]. The Barium hexaferrite is widely used due to its thermal, electrical and chemical high stability and high remanence and coercivity [2]. In general, they can be classified into two categories: isotropic and anisotropic ferrites. In the case of isotropic magnets, the material shows random orientation of the c-axis of the grains and has equal magnetic properties in all directions. The remanence Br and coercive force Hc of ferrite magnets are around 2 kG and 1.5 to 20 kOe, respectively, depending on the processing of the ferrite material. For anisotropic hard ferrite magnets, enhancement of remanent magnetization of the material is obtained by orientating of the c-axis of the plate-like hexagonal ferrite crystals to the direction of an external magnetic field that was applied during the shaping process of the material. The remanent magnetization of anisotropic ferrite is nearly twice the value of the isotropic ones [3].

  19

  12 O

  19

  Abstract. The objective of present work is to investigate the characteristic of BaFe ₁₂ O ₁₉ , B ₂ O ₃ -BaFe ₁₂ O ₁₉ and Fe- BaFe ₁₂ O ₁₉ magnets fabricated at different milling time and sintering temperature. The characteristic of perrmanen magnet BaFe ₁₂ O ₁₉ with different content of B ₂ O ₃ and Fe which was fabricated at different milling time and sintering temperature

were investigated. The powder mixtures were prepared by dry and wet milling at various milling time. The powder were

mixtured and prepared by dry and wet milling at various milling time. The mixture powder was then compacted by

anisotropic with compressive pressure of 50 N/cm ² . The green bodies were sinter at 1050, 1100, 1150 and 1200 ^o C and

hold for 1 h, separately. The density, magnetic flux density and B-H curve were measured by Archimedes principle,

  12 O

  (M = Ba, Sr, Pb or mixture of them) [1]. Especially barium and strontium hexaferrites (Ba.Fe

  3

  2 O

  (M = Ba, Sr, Pb or mixture of them) [1].The hard ferrite magnets M series are experessed as M.O6Fe

  3 additives for obtaining desired structural and magnetic properties in the ferrite magnets [3]. Ceramic-metal nanocomposites have also received increasing attention because of their unique mechanical, electrical and magnetic properties. Previous works [4, 5] have successfully prepared the magnetic ceramic-metal nanocomposites, such as BaFe O /Fe magnetic composite by using high energy ball milling. This material has shown interesting magnetic

  2 Postgraduate Program, Faculty of Mathematic and Natural Science, University of Sumatera Utara-Indonesia,

20155

  Generally, the hard ferrite magnets are expressed as M.O6Fe

  

INTRODUCTION

  

Gauss meter and Permagraph, respectively. The microstructure and phase composition characterization were performed

by SEM and XRD. The results of this study are presented in this paper. It shows that addition of Fe (in wet milling) and

B ₂ O ₃ (in dry milling) respectively give a potential benefit to reduce the sintering temperature and improve the magnetic flux density of barium hexaferrite.

  2 O

  12

  19 properties, with potential for some industrial applications.

  For powder preparation, commercial milling techniques are used in magnetic materials technology to reduce the particle size from multidomain to single domain direction. The effect of milling and annealing on intrinsic coercivity of BaFe O powder has been studied for dry-milled and wet-milled powder. In both cases, it was observed that

  12

  19 prolonged milling decreases both coercivity and magnetic saturation [6].

  In this work, the synthesis and characterization of structure and magnetic properties of sintered BaFe O with

  12

  19 various B O and Fe additives were carried out. The goals of this work is to study the effect of milling time under

  2

  3 dry and wet milling condition, sintering temperature and the addition of B O and Fe on physical and magnetic

  2

  3 properties of BaFe O permanent magnets. The particle size analyzer (PSA), X-ray diffraction (XRD), scanning

  12

  19 electron microscope (SEM), Gauss meter and permagraph have been used to investigate and analyze the aforementioned magnetic material.

EXPERIMENTAL PROCEDURES

  The raw material used in this study is a commercial Barium hexaferrite (BaFe O ) powder and additives of

  12

  19 B O and Fe powder. Their weight ratio-percentage is shown in Table 1. At the first step of this work, in order

  2

  3 tostudy the effect of milling time and sintering temperature, 20 gram of BaFe O were milled by using High

  12

  19 Energy Milling (HEM) at various milling time under wet and dry milling condition, separately. The milling process was carried out by using stainless steel ball and jar mill with ball and powder ratio of 10:1 at 120 rpm.

  

TABLE 1. Weight ratio percentage of BaFe O , B O and Fe.

  12

  19

  2

  3 Weight ratio percentage of Weight ratio percentage of

  BaFe O B O BaFe O Fe

  12

  19

  2

  3

  12

  19 BaFe O : B O (wt%) (gram) (gram) BaFe O : Fe (wt%) (gram) (gram)

  12

  19

  2

  3

  12

  19

  100.0 : 0.2

  19.96 0.04 99 : 1

  19.8

  0.2 99.5 : 0.5

  19.9 0.1 95 : 5

  19.0

  1.0 99.0 : 1.0

  19.8 0.2 90 : 10

  18.0

  2.0 98.0 : 2.0

  19.6 0.4 80 : 20

  16.0

  4.0 In the wet milling method, the process was carried out for 0, 10, 20, and 40 hours and for the dry milling method, the process was performed for 12, 24, 48 and 60 hours. The particle size and true density of original powder and milled powder were measured by particle size analyzer (PSA) and picnometer, respectively. From the both process, the optimum milling time were obtained. In the second step of this study, we also considered the addition of varying amount of B O (0.2, 0.5, 1, 2 wt%) and Fe (1, 5, 10, 20) in order to improve the physical and magnetic properties

  2

  3 of barium hexaferrite. The milling time was fixed according to the optimum aforementioned condition: 48 h for dry milling time of B O addition and 20 h for wet milling time of Fe addition. The powder were then dried in an oven

  2

  3 at 100 C for 1h, mixed with 3 wt% Celuna (WE-158) and compacted by using magnetic field press (anisotropic

  2 process) at 50 N/cm press. The molding dies are made from steainless steel with 12 mm in diameter. 2 gram of powder was used for each sample.

  The sintering temperature was identified from sintering shrinkage curve which shows the correlation between temperature and shrinkage of the sample [7]. In this research, the temperature for sintering was selected at elevated o o o temperatures of 1100

  C, 1150 C and 1200 C with 1 hour in holding time. The optimation of sintering temperature can be known based on bulk density value which is measured by using Archimedes method (ASTM C. 373-88- 2006). The phase composition was analyzed by X-Ray Diffraction (XRD) and morphology of specimens was studied by using a Scanning Electron Microscope (SEM). The magnetic properties (B-H curve) were obtained from permagraph equipment of Magnet Physik and the magnetic flux density is measured by using Gauss meter.

  

RESULTS AND DISCUSSION

The effects of Milling Time and Sintering Temperature

  True density and average particle size of barriumhexaferrite powder before and after milling under wet and dry milling condition with varying milling time of 10, 20, 40 and 12, 24, 48, 60, respectively are shown in FIGURE 1.

  (a).

  (b). FIGURE 1.True density and average particle size of BaFe O prepared at varying milling time under (a) wet milling and

  12

  19

(b)dry milling conditions.

  3 BaFe O According to the results shown in Figure 1, the true density and particle size of are around 4.37g/cm

  12

  19 and 21.4µm, respectively. As the milling time increase, the true density increases and the average particle size tends to decrease. The optimum true density and average particle size of barium hexaferrite were achieved at 20 h for wet

  3

  3 milling (4.70 g/cm and 7.56 µm) and 48 h for dry milling (4.76 g/cm and 3.97 µm). For dry milling, at milling time more than 48 hours (Fig. 1b ), the powder seems to become agglomeration. The results of this study suggest that in both conditions, the true density and particle size of BaFe O powder show an opposite behavior. In

  12

  19 addition, the results show that as the milling time increases, the the average particle size of powder has a tendency to decrease.

  Table 2 shows the bulk density and magnetic flux density of original BaFe O , wet and dry milled powder

  12

  19 o o o sintered at 1100 C, 1150 C and 1200 C for one-hour holding time.

  

TABLE 2.Bulk density and magnetic flux density of BaFe O magnets with and without milling.

  12

  19 Sintering Original powder Wet milling (20 h) Dry milling (48 h)

  Bulk density Magnetic flux Bulk density Magnetic flux Bulk density Magnetic flux condition

  3

  

3

  3

(g/cm ) (g/cm ) (g/cm )

density density density

  (gauss) (gauss) (gauss) o 1100

  C, 1 h

  4.86 760 4.61 620 4.63 798.5

  o

  1150

  C, 1 h

  4.88 744 4.71 594 4.56 617

  o 1200

  C, 1 h

  4.98 786 4.66 609 4.55 744 The optimum bulk density of compact-original powder, wet milled and dry milled powder is 4.98, 4.71 and 4.63

  3 g/cm , respectively. The magnetic flux densities at the aforesaid density are 786, 594 and 798.5 Gauss, respectively.

  The results as presented in Table 2 indicate that there isn’t strong correlation between bulk density and magnetic flux density. Specimen that has optimum bulk density does not always have optimum magnetic flux density. This could be related to the presence of pores which reduces the magnetic flux density of barium hexaferrite.

  Figure 2 shows the SEM images of original, wet and dry milled barium hexaferrite powder sintered at 1200, o 1150 and 1100 C for 1h, respectively.

• 5wt% Fe after wet milling process for 20 hours and BaFe
• 0.5wt% B

  sample with B

  4.78 m

  4.8

  4.74

  4.71 d e n sit y

  4.62

  4.6

  4.55

  u lk

Fe additive

B2O3 additive

  4.4

1050 1100 1150 1200

  Sintering temperature ( o

  C) FIGURE 3.Correlation of sintering temperature versus bulk density of BaFe

  12 O

  19

  2 O

  4.86

  3 and Fe addition.

  The bulk densities of specimens were 4.86 g/cm

  3 for 0.5 wt% B

  2 O

  3 addition and 4.78g/cm

  3 for 5 wt% Fe additions. In general, the bulk density of material shows a linear correlation with sintering temperature. However, it tend to decrease when deformation of material take places (> sintering temperature). The bulk density of material decreases due to the grain of particles growth and enlargement of pores in grain boundaries. Meanwhile, the magnetic flux density of material is affected by oriented particle in c-axis [3].

  The bulk density and magnetic flux density of BaFe

  12 O

  19 sample as a function of Fe content: 0, 1, 5, 10 and

  20wt% sintered at 1150 o

  C for 1 h and B

  2 O

  3 content : 0, 0.2, 0.5, 1.0 and 2.0 wt% sintered at 1100 o

  C for 1 h are summarized in Fig. 4a and 4b, respectively.

  3

  5 )

  

(a). (b). (c).

  The Effects of Fe and B

  FIGURE 2.SEM image of sintered a) BaFe

  12 O

  19

  powder, b) BaFe

  12 O

  19

  powder after wet milling for 20 h and c) BaFe

  12 O

  19

  powder after dry milling for 48 h .

  As can be seen in Fig. 2, BaFe

  12 O

  19 powder without milling process has grain size about 2-6µm. For 48 h dry milling sample, the specimen has a bigger grain size among before milling and sintered wet milled powder. This suggests that the dry milling process seems to enhance the grain growth of barium hexaferrite.

  2 O

  3 and 5 wt% Fe addition is 1100 and 1150 o C for 1 h, respectively.

  3 Additions

  The average particle size of BaFe

  12 O

  19

  12 O

  19

  2 O

  3 after dry milling process for 48h is 3.73 µm and 1.10 µm , respectively.

  Figure 3 shows the correlation between sintering temperature and bulk density of BaFe

  12 O

  19 with B

  2 O

  3 and Fe addition. The sintering temperature was determined from the optimum bulk density of specimen. Therefore, it can be seen that the optimum sintering temperature for barium hexaferrite with 0.5 wt% B

  2 O

4.54 B

  (a).

  (b). FIGURE 4.Bulk density and magnetic flux density of BaFe O sample with the addition of (a) Fe (wt%)-sintered

  12

  19 o o

  

at1150 C for 1 h, and b) B O (wt%)-sintered at 1100 C for 1 h.

  2

  3 The results show that the optimum bulk density and magnetic flux density are obtained by 5 wt% Fe addition

  3

  3 (4.78 g/cm and 883 Gauss) and 0.5wt% B O addition (4.86 g/cm and 832.9 Gauss). Comparing the magnetic flux

  2

  3 density of sintered original powder, it suggests that the addition of B O and Fe can improve the magnetic flux

  2

  3 density and decrease the sintering temperature of barium hexaferrite. The SEM images of BaFe O with 0.5 wt%

  12

  19 B O and 5 wt% Fe additions are shown in the Fig. 5a and 5b, respectively.

  2

  3 (a). (b). o FIGURE 5.SEM image of a). BaFe O -5wt%Fe sintered at 1150 C and b).

  12

  19 o

  BaFe O -0.5wt%B O sintered at 1100 C

  12

  19

  2

  3 A different in grain size: large and small grain can be distinguished clearly in the sintered BaFe O with 5wt%

  12

  19 Fe addition. Meanwhile in the sintered BaFe O -0.5wt%B O , the material shows more homogeneous

  12

  19

  2

  3 microstructure.

  X-ray diffraction patterns of original BaFe O BaFe O -5wt%Fe and BaFe O -0.5wt%B O are shown in 12 19,

  12

  19

  12

  19

  2

  3 Fig. 6. According to the results as shown above, sintered original powder is composed of single phase of BaFe O .

  12

  19 On the other hand, two phases as BaFe O and hematite (Fe O ) phases were detected in the barium hexaferrite

  12

  19

  2

  3 with 0.5 wt% B O and with 5 wt% Fe addition. This indicates that the addition of 0.5 wt% B O and 5wt% Fe

  2

  3

  2

  3 leads to the formation of hematite.

  Table 3 presents the remanence B , coercivityH and energy product BH of BaFe O , BaFe O -0.5 wt% r cj max

  12

  19

  12

  19 o B O and BaFe O -5 wt% Fe sintered at 1100C, and 1150 C for 1 h, respectively.

  2

  3

  12

  19 TABLE 3.Magnetic properties of BaFe O with B O and Fe addition

  12

  19

  2

  3 Sample Remanence, Coercivity, Energy product,

  BH (MGOe) Br (kG) Hc (kOe) max

  o BaFe O (original)-1200 C, 1h.

  12

  19 2.26 2.903

  1.06 o

  BaFe O +0.5 wt% B O -1100 C, 1 h.

  12

  19

  2

  3 2.28 2.435

  1.05 o

  BaFe O +5 wt% Fe-1150 C, 1 h.

  12

  19 2.25 3.479

  1.07 o

  FIGURE 6. XRD patterns of (a) original BaFe O powder sintered at 1200

  C, (b) 5 wt% B O added-BaFe O (dry milled

  12

  19

  2

  3

  12

  19 o o for48 h and sintered at 1100 C for 1 h), c) 5 wt% Fe added-BaFe O (wet milled for 20 h and sintered at 1150 C for 1h.

  12

  19 The results indicate that the remanence B , coercivityH and energy product BH of barium hexaferrite with 5 r cj max o wt% Fe addition sintered at 1150 C for 1 h are 2.25 kG, 3.479 kOe and 1.07 MGOe, respectively. On the other o hand, the aforementioned properties of barium hexaferrite with 0.5 wt% B O addition sintered at 1100 C for 1 h

  2

  3 o are 2.28 kG, 2.435 kOe and 1.05 MGOe, respectively. For BaFe O samples without milling sintered at 1200 C

  12

  19 for 1 h, the magnetic properties are as follows: magnetic remanence, B = 2.26 kG, coercivity, H = 2.903 kOe and r cj energy product, BH = 1.06 MGOe. max

  

Summary

  In this study, the effects of milling time and sintering temperature on the physical and magnetic prop erties of barium hexaferrite have been performed. In addition, in order to improve the properties of barium hexaferrite, the addition of Fe (wet milling) and B O (dry milling) has also been carried out. The most important finding of this

  2

  3 study is that the addition of Fe and B O with wet and dry milling process, respectively give a potential benefit to

  2

  3 reduce the sintering temperature and improve the magnetic flux density of barium hexaferrite.

  

ACKNOWLEDGMENTS

  This work was supported by Research Center for Physics, Indonesian Institute of Sciences under contract DIPA 2014 (No. 0131/IPT.1.03/A/2014).

  

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