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Comparative study of structural and magnetic properties of NiZnCu ferrite powders prepared via chemical coprecipitation method with different coprecipitators
Journal of Magnetism and Magnetic Materials 323 (2011) 1682–1685
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Comparative study of structural and magnetic properties of NiZnCu ferrite powders prepared via chemical coprecipitation method with different coprecipitators Ailin Xia n, Chuangui Jin, Dexin Du, Guohui Zhu Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 27 September 2010 Received in revised form 19 January 2011 Accepted 24 January 2011 Available online 12 February 2011
We prepared NiZnCu ferrite powders with nominal composition Ni0.4 xZn0.6CuxFe2O4 (x ¼ 0–0.2) via chemical coprecipitation method with NaOH and Na2CO3 as coprecipitators. The structural and magnetic properties of these compounds were studied and compared. It is found that all the specimens exhibit single-phase structure after annealing. The saturation magnetization of specimens with NaOH as coprecipitator is lower than that with Na2CO3 as coprecipitator. It is also found that the growth of grains is hindered for specimens using Na2CO3 as coprecipitator. & 2011 Elsevier B.V. All rights reserved.
Keywords: NiZnCu ferrite Chemical coprecipitation method Coprecipitator Structural and magnetic properties
1. Introduction In recent years, as one of the key materials for manufacturing multilayer chip inductors, NiZnCu ferrite has been widely studied via traditional ceramic method [1–6], sol–gel method [7–9], chemical coprecipitation method [10–14], auto-combustion method [15–17] and other newly developed methods [18,19], since it is suitable for sintering at low temperature. For chemical coprecipitation method, NaOH or (NH4)2C2O4 H2O was usually used as coprecipitator to prepare NiZnCu ferrite powders. In the mixed coprecipitated powders, Zn(OH)2 is a kind of amphoteric compound that can be dissoved in alkaline solution. However, as is known, the coprecipitation reactions just occur in strong alkaline solution. Moreover, Zn2 + is easy to form complex [Zn(NH3)4]2 + ion. Therefore, if using NaOH or (NH4)2C2O4 H2O as coprecipitator, the precipitation of Zn2 + ions may be incomplete. We have studied the effects of excessive Zn2+ ions on the intrinsic magnetic and structural properties of Ni0.2Zn0.6Cu0.2Fe2O4 powder prepared by chemical coprecipitation method [10], and found that increasing the Zn2+ content suitably according to the nominal composition was effective to decrease the effect of incomplete precipitation of Zn2 + ions. However, the process is difficult to control accurately due to the complexity of different coprecipitation processes. Therefore, choosing a more suitable coprecipitator may be a good choice. Comparably, alkalinity of Na2CO3 is weaker than that
n
Corresponding author. Tel.: +86 013665557919; fax: + 86 0555 2311570. E-mail address: [email protected] (A. Xia).
0304-8853/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2011.01.037
of NaOH, and it will not form any complex ions with Zn2+ or other ions. Therefore, using Na2CO3 as coprecipitator may be a better choice for the preparation of NiZnCu ferrites. In this study, we report the results of NiZnCu ferrite powders prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitator. The structural and magnetic properties of these powder specimens with both coprecipitators are studied and compared.
2. Experimental procedure NiZnCu ferrite powders with nominal composition Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) were prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitators. After the coprecipitation reaction, the mixed powders obtained were washed and then dried at 180 1C for 10 h to form spinel structure preliminarily [20]. Then, all the precursor powders were annealed at 900 1C for 3 h to form spinel structure completely. For convenience, the annealed powders obtained using NaOH (Na2CO3) as coprecipitator are named as H (C) specimens. The crystalline structures of powder specimens were determined by a Bruker D8 X-ray diffractometer (XRD) with Cu Ka radiation ˚ The magnetic hysteresis loops were measured by (l ¼1.5418 A). a Lakeshore 7410 vibrating sample magnetometer (VSM) with a maximum external field Hm E1114 kA m 1 ( 14,000 Oe). The micrographs were obtained by a JEOL JSM-6490LV scanning electron microscopy (SEM).
A. Xia et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1682–1685
3. Results and discussion 3.1. Crystalline structures
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precursor powders before annealing were captured with XRD and are given in Fig. 6. It is observed that the spinel structure is partly formed in the precursor powders after drying at 180 1C for 10 h for specimens with both coprecipitators. For H precursor
Fig. 1 shows the XRD patterns of annealed Ni0.4 xZn0.6CuxFe2O4 (x ¼0, 0.05, 0.10, 0.15, 0.20) powder specimens prepared. Obviously, Fig. 1(a) and (b) reveals the same information of typical spinel structure, which means all the H and C specimens are single-phase spinel structure after annealing. Therefore, the specimens can form a single-phase spinel structure using either NaOH or Na2CO3 as coprecipitator. 3.2. Magnetic properties Fig. 2 gives the magnetic hysteresis loops of annealed Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) powder specimens. The typical magnetic properties (Saturation magnetization: Ms; Coercivity: Hc) are listed in Table 1. Obviously, all the specimens exhibit typical soft-magnetic behaviors. Fig. 3 illustrates the variation of Ms for both H and C specimens. Obviously, for either H or C specimens, the Ms decreases with increasing Cu content x, which is consistent with the previously reported results [13,21]. However, seen from Fig. 3, it is found that the Ms of C specimens is obviously better than that of corresponding H specimens with same x. We contribute this to the facilitated precipitation of Zn2 + ions when using Na2CO3 as coprecipitator, which helps to form the stoichiometric powders. 3.3. Microstructures In order to study the difference of microstructures between the H and C specimens, the micrographs of powder specimens were checked by SEM, and those of typical specimens with x ¼0.05 and 0.10 are shown in Fig. 4. Comparing Fig. 4(a) with (b) and (c) with (d), the average grain size of powder specimens obviously increases with increasing Cu content x, which can be attributed to the effect of Cu on the decrease of annealing temperature and is consistent with the previous study [12]. What we are really interested in is the difference of microstructures between the H and C specimens with the same x. The histograms of grain size distribution are calculated from Fig. 4 and are shown in Fig. 5. From Figs. 4 and 5, it is found that compared with H specimens, there are obviously much more grains that are smaller than 1 mm in the corresponding C specimens with the same x. In order to study further, the structure information of the
Fig. 2. Magnetic hysteresis loops of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
Table 1 Magnetic properties of Ni0.4 xZn0.6CuxFe2O4 ferrite powders prepared by different coprecipitators. Coprecipitator
x
Ms (emu/g)
Hc (A/m)
NaOH
0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20
66.17 56.99 56.61 54.19 52.12 66.36 58.71 57.90 56.17 53.30
1393 358 613 326 o 320 1879 924 613 390 o 320
Na2CO3
Fig. 1. XRD patterns of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
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powders, seen from Fig. 6(a), except for some Zn(OH)2 (PDF: 20– 1435) impurity peaks, the spinel structure is almost formed. However, for C precursor powders, stronger Zn(OH)2 peaks can be seen in Fig. 6(b). On the one hand, this means the spinel structure is more difficult to form in C precursor powders, but on the other hand, it also can be deduced that Zn2 + ions were precipitated better. As is known, the decomposition temperatures of Zn(OH)2, Cu(OH)2 and Ni(OH)2 are about 120, 140 and 230 1C, respectively, and Fe(OH)3 can be decomposed gradually if heated at room temperature till 180 1C, a temperature at which it can be decomposed completely. In this study, the mixed H precursor powders after coprecipitation reaction consist of hydroxides, such as Zn(OH)2, Cu(OH)2, Ni(OH)2 and Fe(OH)3. Therefore, after drying at 180 1C for
10 h, most hydroxides except Ni(OH)2 will be decomposed into oxides of high activity, which promotes the solid-state reaction and helps the formation of spinel structure at low temperatures. This explains the XRD pattern of similar spinel structure except for some peaks from Zn(OH)2 exhibited in Fig. 6(a). However, it is not the case for C precursor powders. After careful analysis, it is found that there are some peaks that can be attributed to carbonates from XRD pattern, for example, CuCO3 marked in Fig. 6(b), since the decomposition temperatures of most carbonates in our case are greater than 180 1C. However, some peaks from carbonates may be covered due to the broadening effects or relatively weak signals from these components. Namely, a great amount of carbonates of low activity can exist in the C precursor powders after drying. These carbonates can not only affect the solid-state reaction during the process of drying, but also release a lot of CO2 gas when annealed at 900 1C, which is sure to increase the porosity and hinder the growth of grains in C specimens. Consequently, compared with H specimens, the existence of much more smaller grains in the corresponding C specimens with the same x is rational.
4. Conclusions
Fig. 3. Variation tendency of saturation magnetization of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with different coprecipitators.
Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) ferrite powders were prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitators, and the structural and magnetic properties were studied and compared. As a result, it is found that using either NaOH or Na2CO3 as coprecipitator, all the specimens exhibit single-phase structure after annealing at high temperature; the saturation magnetization of specimens using NaOH as coprecipitator is lower than that of specimens using Na2CO3 as coprecipitator, which proves that Na2CO3 can help to form the stoichiometric powders. Further, compared with H specimens, there are much more small grains in the corresponding C specimens with the same x, which can be attributed to the existence of carbonates in the precursor powders.
Fig. 4. SEM micrographs of typical Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h. (a, c): x¼ 0.05, (b, d): x ¼0.10; (a, b): NaOH, (c, d): Na2CO3 coprecipitator.
A. Xia et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1682–1685
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Fig. 5. Histograms of grain size distribution of typical Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h. (a, c): x¼ 0.05, (b, d): x¼ 0.10; (a, b): NaOH, (c, d): Na2CO3 coprecipitator.
Fig. 6. XRD patterns of Ni0.3Zn0.6Cu0.1Fe2O4 precursor powders before annealing prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
Acknowledgements This work was supported by the Foundation for Young Talents of Anhui Province, China, under Grant no. 2009SQRZ074ZD and the National Natural Science Foundation of China under Grant no. 21071003. References [1] W.W. Ling, H.W. Zhang, Y. He, Y. Wu, K. Yang, Y.X. Li, S. Li, Low temperature fired Ni–Cu–Zn ferrite with Bi4Ti3O12, J. Magn. Magn. Mater. 322 (2010) 819–823. [2] M. Kaiser, Influence of V2O5 ion addition on the conductivity and grain growth of Ni–Zn–Cu ferrites, Curr. Appl. Phys. 10 (2010) 975–984. [3] D. Sakellari, V. Tsakaloudi, E.K. Polychroniadis, V. Zaspalis, Microstructural phenomena controlling losses in NiCuZn-ferrites as studied by transmission electron microscopy, J. Am. Ceram. Soc. 91 (2008) 366–371.
[4] R.T. Hsu, J.H. Jean, Y.Y. Hung, Stress required to densify a low-fire NiCuZn ferrite under constrained sintering, J. Am. Ceram. Soc. 91 (2008) 2051–2054. [5] X.C. Liu, F. Gao, C.S. Tian, Numerical simulation of diffusion ions in ZnTiO3 dielectrics/NiZnCu ferrite composites using restricted shrinkage sintering process, Solid State Sci. 10 (2008) 211–216. [6] D. Sakellari, N. Frangis, E.K. Polychroniadis, A self-organized nanostructure induced by phase separation in NiCuZn-ferrites, Physica E 42 (2010) 1777–1780. [7] N.J. Chu, X.Q. Wang, Y.P. Liu, H.X. Jin, Q. Wu, L. Li, Z.S. Wang, H.L. Ge, Magnetic properties of low Mn-doped NiCuZn nanocrystalline ferrites, J. Alloy. Compd. 470 (2009) 438–442. [8] F. Liu, C. Yang, T.L. Ren, A.Z. Wang, J. Yu, L.T. Liu, NiCuZn ferrite thin films grown by a sol–gel method and rapid thermal annealing, J. Magn. Magn. Mater. 309 (2007) 75–79. [9] P.K. Roy, J. Bera, Enhancement of the magnetic properties of Ni–Cu–Zn ferrites with the substitution of a small fraction of lanthanum for iron, Mater. Res. Bull. 42 (2007) 77–83. [10] A.L. Xia, H.L. Zhang, Effects of excessive Zn2 + ions on intrinsic magnetic and structural properties of Ni0.2Zn0.6Cu0.2Fe2O4 powder prepared by chemical coprecipitation method, Curr. Appl. Phys. 10 (2010) 825–827. [11] H.B. Wang, J.H. Liu, W.F. Li, J.B. Wang, L. Wang, L.J. Song, S.J. Yuan, F.S. Li, Structural, dynamic magnetic and dielectric properties of Ni0.15Cu0.2Zn0.65Fe2O4 ferrite produced by NaOH co-precipitation method, J. Alloy. Compd. 461 (2008) 373–377. [12] W.C. Hsu, S.C. Chen, P.C. Kuo, C.T. Lie, W.S. Tsai, Preparation of NiCuZn ferrite nanoparticles from chemical co-precipitation method and the magnetic properties after sintering, Mater. Sci. Eng. B 111 (2004) 142–149. [13] I.Z. Rahman, T.T. Ahmed, A study on Cu substituted chemically processed Ni–Zn–Cu ferrites, J. Magn. Magn. Mater. 290–291 (2005) 1576–1579. [14] P.K. Chakrabarti, B.K. Nath, S. Brahma, S. Das, D. Das, M. Ammar, F. Mazaleyrat, Magnetic and hyperfine properties of chemically synthesized (Al2O3)x(Ni0.2Zn0.6Cu0.2Fe2O4)(1 x) (x ¼0.15, 0.30, 0.45), Solid State Commun. 144 (2007) 305–309. [15] M.A. Gabal, S.A. Al-Thabaiti, E.H. El-Mossalamy, M. Mokhtar, Structural, magnetic and electrical properties of Ga-substituted NiCuZn nanocrystalline ferrite, Ceram. Int. 36 (2010) 1339–1346. [16] P.A. Jadhav, R.S. Devan, Y.D. Kolekar, B.K. Chougule, Structural, electrical and magnetic characterizations of Ni–Cu–Zn ferrite synthesized by citrate precursor method, J. Phys. Chem. Solids 70 (2009) 396–400. [17] P.K. Roy, J. Bera, Electromagnetic properties of samarium-substituted NiCuZn ferrite prepared by auto-combustion method, J. Magn. Magn. Mater. 321 (2009) 247–251. [18] M.A. Gabal, Y.M. Al Angari, S.S. Al-Juaid, A study on Cu substituted Ni–Cu–Zn ferrites synthesized using egg-white, J. Alloy. Compd. 492 (2010) 411–415. [19] M.A. Gabal, Magnetic properties of NiCuZn ferrite nanoparticles synthesized using egg-white, Mater. Res. Bull. 45 (2010) 589–593. [20] R. Walenzuela, Magnetic Ceramics, Cambridge University, Cambridge, 1994. [21] H.B. Callen, S.E. Harrison, C.J. Kriessman, Cation distributions in ferrospinels. Theoretical, Phys. Rev. 103 (1956) 851–856.
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Comparative study of structural and magnetic properties of NiZnCu ferrite powders prepared via chemical coprecipitation method with different coprecipitators Ailin Xia n, Chuangui Jin, Dexin Du, Guohui Zhu Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 27 September 2010 Received in revised form 19 January 2011 Accepted 24 January 2011 Available online 12 February 2011
We prepared NiZnCu ferrite powders with nominal composition Ni0.4 xZn0.6CuxFe2O4 (x ¼ 0–0.2) via chemical coprecipitation method with NaOH and Na2CO3 as coprecipitators. The structural and magnetic properties of these compounds were studied and compared. It is found that all the specimens exhibit single-phase structure after annealing. The saturation magnetization of specimens with NaOH as coprecipitator is lower than that with Na2CO3 as coprecipitator. It is also found that the growth of grains is hindered for specimens using Na2CO3 as coprecipitator. & 2011 Elsevier B.V. All rights reserved.
Keywords: NiZnCu ferrite Chemical coprecipitation method Coprecipitator Structural and magnetic properties
1. Introduction In recent years, as one of the key materials for manufacturing multilayer chip inductors, NiZnCu ferrite has been widely studied via traditional ceramic method [1–6], sol–gel method [7–9], chemical coprecipitation method [10–14], auto-combustion method [15–17] and other newly developed methods [18,19], since it is suitable for sintering at low temperature. For chemical coprecipitation method, NaOH or (NH4)2C2O4 H2O was usually used as coprecipitator to prepare NiZnCu ferrite powders. In the mixed coprecipitated powders, Zn(OH)2 is a kind of amphoteric compound that can be dissoved in alkaline solution. However, as is known, the coprecipitation reactions just occur in strong alkaline solution. Moreover, Zn2 + is easy to form complex [Zn(NH3)4]2 + ion. Therefore, if using NaOH or (NH4)2C2O4 H2O as coprecipitator, the precipitation of Zn2 + ions may be incomplete. We have studied the effects of excessive Zn2+ ions on the intrinsic magnetic and structural properties of Ni0.2Zn0.6Cu0.2Fe2O4 powder prepared by chemical coprecipitation method [10], and found that increasing the Zn2+ content suitably according to the nominal composition was effective to decrease the effect of incomplete precipitation of Zn2 + ions. However, the process is difficult to control accurately due to the complexity of different coprecipitation processes. Therefore, choosing a more suitable coprecipitator may be a good choice. Comparably, alkalinity of Na2CO3 is weaker than that
n
Corresponding author. Tel.: +86 013665557919; fax: + 86 0555 2311570. E-mail address: [email protected] (A. Xia).
0304-8853/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2011.01.037
of NaOH, and it will not form any complex ions with Zn2+ or other ions. Therefore, using Na2CO3 as coprecipitator may be a better choice for the preparation of NiZnCu ferrites. In this study, we report the results of NiZnCu ferrite powders prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitator. The structural and magnetic properties of these powder specimens with both coprecipitators are studied and compared.
2. Experimental procedure NiZnCu ferrite powders with nominal composition Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) were prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitators. After the coprecipitation reaction, the mixed powders obtained were washed and then dried at 180 1C for 10 h to form spinel structure preliminarily [20]. Then, all the precursor powders were annealed at 900 1C for 3 h to form spinel structure completely. For convenience, the annealed powders obtained using NaOH (Na2CO3) as coprecipitator are named as H (C) specimens. The crystalline structures of powder specimens were determined by a Bruker D8 X-ray diffractometer (XRD) with Cu Ka radiation ˚ The magnetic hysteresis loops were measured by (l ¼1.5418 A). a Lakeshore 7410 vibrating sample magnetometer (VSM) with a maximum external field Hm E1114 kA m 1 ( 14,000 Oe). The micrographs were obtained by a JEOL JSM-6490LV scanning electron microscopy (SEM).
A. Xia et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1682–1685
3. Results and discussion 3.1. Crystalline structures
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precursor powders before annealing were captured with XRD and are given in Fig. 6. It is observed that the spinel structure is partly formed in the precursor powders after drying at 180 1C for 10 h for specimens with both coprecipitators. For H precursor
Fig. 1 shows the XRD patterns of annealed Ni0.4 xZn0.6CuxFe2O4 (x ¼0, 0.05, 0.10, 0.15, 0.20) powder specimens prepared. Obviously, Fig. 1(a) and (b) reveals the same information of typical spinel structure, which means all the H and C specimens are single-phase spinel structure after annealing. Therefore, the specimens can form a single-phase spinel structure using either NaOH or Na2CO3 as coprecipitator. 3.2. Magnetic properties Fig. 2 gives the magnetic hysteresis loops of annealed Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) powder specimens. The typical magnetic properties (Saturation magnetization: Ms; Coercivity: Hc) are listed in Table 1. Obviously, all the specimens exhibit typical soft-magnetic behaviors. Fig. 3 illustrates the variation of Ms for both H and C specimens. Obviously, for either H or C specimens, the Ms decreases with increasing Cu content x, which is consistent with the previously reported results [13,21]. However, seen from Fig. 3, it is found that the Ms of C specimens is obviously better than that of corresponding H specimens with same x. We contribute this to the facilitated precipitation of Zn2 + ions when using Na2CO3 as coprecipitator, which helps to form the stoichiometric powders. 3.3. Microstructures In order to study the difference of microstructures between the H and C specimens, the micrographs of powder specimens were checked by SEM, and those of typical specimens with x ¼0.05 and 0.10 are shown in Fig. 4. Comparing Fig. 4(a) with (b) and (c) with (d), the average grain size of powder specimens obviously increases with increasing Cu content x, which can be attributed to the effect of Cu on the decrease of annealing temperature and is consistent with the previous study [12]. What we are really interested in is the difference of microstructures between the H and C specimens with the same x. The histograms of grain size distribution are calculated from Fig. 4 and are shown in Fig. 5. From Figs. 4 and 5, it is found that compared with H specimens, there are obviously much more grains that are smaller than 1 mm in the corresponding C specimens with the same x. In order to study further, the structure information of the
Fig. 2. Magnetic hysteresis loops of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
Table 1 Magnetic properties of Ni0.4 xZn0.6CuxFe2O4 ferrite powders prepared by different coprecipitators. Coprecipitator
x
Ms (emu/g)
Hc (A/m)
NaOH
0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20
66.17 56.99 56.61 54.19 52.12 66.36 58.71 57.90 56.17 53.30
1393 358 613 326 o 320 1879 924 613 390 o 320
Na2CO3
Fig. 1. XRD patterns of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
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powders, seen from Fig. 6(a), except for some Zn(OH)2 (PDF: 20– 1435) impurity peaks, the spinel structure is almost formed. However, for C precursor powders, stronger Zn(OH)2 peaks can be seen in Fig. 6(b). On the one hand, this means the spinel structure is more difficult to form in C precursor powders, but on the other hand, it also can be deduced that Zn2 + ions were precipitated better. As is known, the decomposition temperatures of Zn(OH)2, Cu(OH)2 and Ni(OH)2 are about 120, 140 and 230 1C, respectively, and Fe(OH)3 can be decomposed gradually if heated at room temperature till 180 1C, a temperature at which it can be decomposed completely. In this study, the mixed H precursor powders after coprecipitation reaction consist of hydroxides, such as Zn(OH)2, Cu(OH)2, Ni(OH)2 and Fe(OH)3. Therefore, after drying at 180 1C for
10 h, most hydroxides except Ni(OH)2 will be decomposed into oxides of high activity, which promotes the solid-state reaction and helps the formation of spinel structure at low temperatures. This explains the XRD pattern of similar spinel structure except for some peaks from Zn(OH)2 exhibited in Fig. 6(a). However, it is not the case for C precursor powders. After careful analysis, it is found that there are some peaks that can be attributed to carbonates from XRD pattern, for example, CuCO3 marked in Fig. 6(b), since the decomposition temperatures of most carbonates in our case are greater than 180 1C. However, some peaks from carbonates may be covered due to the broadening effects or relatively weak signals from these components. Namely, a great amount of carbonates of low activity can exist in the C precursor powders after drying. These carbonates can not only affect the solid-state reaction during the process of drying, but also release a lot of CO2 gas when annealed at 900 1C, which is sure to increase the porosity and hinder the growth of grains in C specimens. Consequently, compared with H specimens, the existence of much more smaller grains in the corresponding C specimens with the same x is rational.
4. Conclusions
Fig. 3. Variation tendency of saturation magnetization of Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h prepared with different coprecipitators.
Ni0.4 xZn0.6CuxFe2O4 (x¼0, 0.05, 0.10, 0.15, 0.20) ferrite powders were prepared via chemical coprecipitation method using NaOH and Na2CO3 as coprecipitators, and the structural and magnetic properties were studied and compared. As a result, it is found that using either NaOH or Na2CO3 as coprecipitator, all the specimens exhibit single-phase structure after annealing at high temperature; the saturation magnetization of specimens using NaOH as coprecipitator is lower than that of specimens using Na2CO3 as coprecipitator, which proves that Na2CO3 can help to form the stoichiometric powders. Further, compared with H specimens, there are much more small grains in the corresponding C specimens with the same x, which can be attributed to the existence of carbonates in the precursor powders.
Fig. 4. SEM micrographs of typical Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h. (a, c): x¼ 0.05, (b, d): x ¼0.10; (a, b): NaOH, (c, d): Na2CO3 coprecipitator.
A. Xia et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1682–1685
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Fig. 5. Histograms of grain size distribution of typical Ni0.4 xZn0.6CuxFe2O4 ferrite powders annealed at 900 1C for 3 h. (a, c): x¼ 0.05, (b, d): x¼ 0.10; (a, b): NaOH, (c, d): Na2CO3 coprecipitator.
Fig. 6. XRD patterns of Ni0.3Zn0.6Cu0.1Fe2O4 precursor powders before annealing prepared with NaOH (a) and Na2CO3 (b) as coprecipitators.
Acknowledgements This work was supported by the Foundation for Young Talents of Anhui Province, China, under Grant no. 2009SQRZ074ZD and the National Natural Science Foundation of China under Grant no. 21071003. References [1] W.W. Ling, H.W. Zhang, Y. He, Y. Wu, K. Yang, Y.X. Li, S. Li, Low temperature fired Ni–Cu–Zn ferrite with Bi4Ti3O12, J. Magn. Magn. Mater. 322 (2010) 819–823. [2] M. Kaiser, Influence of V2O5 ion addition on the conductivity and grain growth of Ni–Zn–Cu ferrites, Curr. Appl. Phys. 10 (2010) 975–984. [3] D. Sakellari, V. Tsakaloudi, E.K. Polychroniadis, V. Zaspalis, Microstructural phenomena controlling losses in NiCuZn-ferrites as studied by transmission electron microscopy, J. Am. Ceram. Soc. 91 (2008) 366–371.
[4] R.T. Hsu, J.H. Jean, Y.Y. Hung, Stress required to densify a low-fire NiCuZn ferrite under constrained sintering, J. Am. Ceram. Soc. 91 (2008) 2051–2054. [5] X.C. Liu, F. Gao, C.S. Tian, Numerical simulation of diffusion ions in ZnTiO3 dielectrics/NiZnCu ferrite composites using restricted shrinkage sintering process, Solid State Sci. 10 (2008) 211–216. [6] D. Sakellari, N. Frangis, E.K. Polychroniadis, A self-organized nanostructure induced by phase separation in NiCuZn-ferrites, Physica E 42 (2010) 1777–1780. [7] N.J. Chu, X.Q. Wang, Y.P. Liu, H.X. Jin, Q. Wu, L. Li, Z.S. Wang, H.L. Ge, Magnetic properties of low Mn-doped NiCuZn nanocrystalline ferrites, J. Alloy. Compd. 470 (2009) 438–442. [8] F. Liu, C. Yang, T.L. Ren, A.Z. Wang, J. Yu, L.T. Liu, NiCuZn ferrite thin films grown by a sol–gel method and rapid thermal annealing, J. Magn. Magn. Mater. 309 (2007) 75–79. [9] P.K. Roy, J. Bera, Enhancement of the magnetic properties of Ni–Cu–Zn ferrites with the substitution of a small fraction of lanthanum for iron, Mater. Res. Bull. 42 (2007) 77–83. [10] A.L. Xia, H.L. Zhang, Effects of excessive Zn2 + ions on intrinsic magnetic and structural properties of Ni0.2Zn0.6Cu0.2Fe2O4 powder prepared by chemical coprecipitation method, Curr. Appl. Phys. 10 (2010) 825–827. [11] H.B. Wang, J.H. Liu, W.F. Li, J.B. Wang, L. Wang, L.J. Song, S.J. Yuan, F.S. Li, Structural, dynamic magnetic and dielectric properties of Ni0.15Cu0.2Zn0.65Fe2O4 ferrite produced by NaOH co-precipitation method, J. Alloy. Compd. 461 (2008) 373–377. [12] W.C. Hsu, S.C. Chen, P.C. Kuo, C.T. Lie, W.S. Tsai, Preparation of NiCuZn ferrite nanoparticles from chemical co-precipitation method and the magnetic properties after sintering, Mater. Sci. Eng. B 111 (2004) 142–149. [13] I.Z. Rahman, T.T. Ahmed, A study on Cu substituted chemically processed Ni–Zn–Cu ferrites, J. Magn. Magn. Mater. 290–291 (2005) 1576–1579. [14] P.K. Chakrabarti, B.K. Nath, S. Brahma, S. Das, D. Das, M. Ammar, F. Mazaleyrat, Magnetic and hyperfine properties of chemically synthesized (Al2O3)x(Ni0.2Zn0.6Cu0.2Fe2O4)(1 x) (x ¼0.15, 0.30, 0.45), Solid State Commun. 144 (2007) 305–309. [15] M.A. Gabal, S.A. Al-Thabaiti, E.H. El-Mossalamy, M. Mokhtar, Structural, magnetic and electrical properties of Ga-substituted NiCuZn nanocrystalline ferrite, Ceram. Int. 36 (2010) 1339–1346. [16] P.A. Jadhav, R.S. Devan, Y.D. Kolekar, B.K. Chougule, Structural, electrical and magnetic characterizations of Ni–Cu–Zn ferrite synthesized by citrate precursor method, J. Phys. Chem. Solids 70 (2009) 396–400. [17] P.K. Roy, J. Bera, Electromagnetic properties of samarium-substituted NiCuZn ferrite prepared by auto-combustion method, J. Magn. Magn. Mater. 321 (2009) 247–251. [18] M.A. Gabal, Y.M. Al Angari, S.S. Al-Juaid, A study on Cu substituted Ni–Cu–Zn ferrites synthesized using egg-white, J. Alloy. Compd. 492 (2010) 411–415. [19] M.A. Gabal, Magnetic properties of NiCuZn ferrite nanoparticles synthesized using egg-white, Mater. Res. Bull. 45 (2010) 589–593. [20] R. Walenzuela, Magnetic Ceramics, Cambridge University, Cambridge, 1994. [21] H.B. Callen, S.E. Harrison, C.J. Kriessman, Cation distributions in ferrospinels. Theoretical, Phys. Rev. 103 (1956) 851–856.