Formation mechanism of nano-crystalline ²-Fe particles with
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Journal of Physics: Conference Series OPEN ACCESS Formation mechanism of nano-crystalline β-Fe 2 O 3 particles with bixbyite structure and their magnetic properties To cite this article: T Danno et al 2010 J. Phys.: Conf. Ser. 200 082003 View the article online for updates and enhancements. You may also like Mechanical characteristics of metal nanoparticle thin film on flexible substrate exposed to saline solution Sanghyeok Kim, Jaeho Park, Jinjae Lee et al. - Comment on “Electrochemical Noise Analysis of Iron Exposed to NaCl Solutions of Different Corrosivity” [J. Electrochem. Soc., 140, 2205] D. A. Eden - Real-Time AFM and Impedance Corrosion Monitoring of Environmentally Friendly Ceria Films on AA7075 Sanja I. Stevanovi, Maria Lekka, Alex Lanzutti et al. - Recent citations Magnetic Nanoparticles; Synthesis, Properties and Electrochemical Application: A Review Maryam Roostaee and Iran Sheikhshoaie - Magnetic Properties of Two-Phase Borosilicate Glasses Containing -Fe2O3 and Fe3O4 Nanoparticles S. A. Borisov et al - Paving the road toward the use of -Fe2O3 in solar water splitting: Raman identification, phase transformation and strategies for phase stabilization Zhigang Zou et al - This content was downloaded from IP address 187.181.54.77 on 12/10/2021 at 22:42
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Formation mechanism of nano-crystalline ββββ-Fe2O3 particles with bixbyite structure and their magnetic properties
T. Danno1, H. Asaoka1, M. Nakanishi1, T. Fujii1, Y. Ikeda2, Y. Kusano3,
J. Takada1 1Department of Material Chemistry, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan 2 Institute of Chemistry Research, Kyoto University, Kyoto 611-0011, Japan 3 Department of Applied Arts and Design, Kurashiki University of Science and the Arts, Kurashiki, Okayama 712-8505, Japan
E-mail:[email protected]
Abstract. Formation mechanism of nano-crystalline β-Fe2O3 particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO4)2 to NaCl and heating treatment temperature. A single phase of β-Fe2O3 was formed regardless of the mixing ratio. The heat treatment temperature strongly affected the particle shapes and sizes. Below 490 , they had granular shape with a diameter of about 50 to 100 nm. While, above 490 , cubic particles with increased size of about 1 µm were produced. All samples were antiferromagnetic at low temperature. The Néel temperature (TN) of 119 K for the large cubic particles was decreased to 113 K for the nanoparticles.
1. Introduction β-Fe2O3 discovered by Bonnevie-Svendsenat at 1956 is one of the polymorphs of iron () oxides [1]. Ιt is known as metastable phase of iron oxides below 770 K. β-Fe2O3 has a body-centered cubic
(bixbyite) structure with a space group of Ia3. The lattice parameter is a0=9.398 [2]. The cubic unit contains 24 Fe3+ ions with C2 symmetry (d site) and 8 ions with C3i Symmetry (b site) [3-5]. The Néel temperature (TN) of magnetic transition was reported between 110 K and 119 K [2,3]. β-Fe2O3 transforms into α-Fe2O3 above 770 K [3,5].
There are several reports about the preparation of β-Fe2O3 [1-9]. However there are only few reports obtaining the single phase β-Fe2O3 [2] and concerning about the magnetic properties of β- Fe2O3 [2,3]. According to ref. [2], β-Fe2O3 was made from the mixtures of Fe2(SO4)3 and NaCl heated at about 500 . However, the formation mechanism and magnetic properties of β-Fe2O3 were still unrevealed. We have already succeeded to prepare the single phase of β-Fe2O3 from the mixture of NaFe(SO4)2 and NaCl . We should mention here that NaFe(SO4)2 was one of the intermediate products in the way of the direct reaction between Fe2(SO4)3 and NaCl. In this paper, we investigate the formation mechanism of β-Fe2O3 by controlling the mixing ratio of NaFe(SO4)2 and NaCl, and also by
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
c© 2010 IOP Publishing Ltd 1
controlling heating conditions. The effects of preparation condition on magnetism for obtained samples will be investigated.
2. Experimental The starting materials were the reagent grade of NaCl, Na2SO4 and Fe2(SO4)3. NaFe(SO4)2 was obtained by evaporating the aqueous solution containing Na2SO4 and Fe2(SO4)3. After that, various amount of NaCl was added to NaFe(SO4)2 and thoroughly mixed in an alumina mortar. The mixtures put in an alumina crucible were heated in the air under the various temperatures for 1 hour. After cooling down to room temperature, the reaction products were dispersed in distilled water and filtered. Phase identification was done by X-ray diffraction (XRD) method in a Rigaku Rint-2000 using CuKα radiation. Morphological properties such as article shapes and sizes were observed by field-emission scanning electron microscopy (FE-SEM, HITACHI S-4300). Magnetic properties of them were characterized by SQUID magnetometer (Quantum Design MPMS2) and Mössbauer spectroscopy.
3. Results and Discussion When a mixture of NaCl and NaFe(SO4)2 was heated in the air above 550 , the final product always contained α-Fe2O3 . Therefore we focused here the heating temperature below 500 . From the differential thermogravimetrical analysis (TG/DTA), the mixture of NaCl and NaFe(SO4)2 was indicated to start reaction at about 320 . This temperature was much lower than the corresponding reaction temperature (about 400 ) of Fe2(SO4)3 with NaCl [2].
Fig. 1 shows XRD patterns of the obtained samples with various mixing ratios after the heat treatment at 500 and washed with the distilled water. The XRD results clearly indicated that the single phase of β-Fe2O3 was produced as a final product regardless of the mixing ratio of NaFe(SO4)2 to NaCl.
Fig. 2 shows XRD patterns of the heat treated samples at difference temperature. The mixing ratio
of NaCl and NaFe(SO4)2 was fixed to 4:1 (molar ratio). Single phase of β-Fe2O3 was obtained at both temperatures. Formation of β-Fe2O3 at 350 is considerably lower than the reaction temperature reported in literatures using Fe2(SO4)3 and NaCl as the starting materials [2,9].
Fig. 1 Typical XRD patterns of the mixture with various ratios heated at 500 and washing with the distilled water
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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Fig. 3 shows the SEM images of β-Fe2O3 particles prepared at 350 and 500 , respectively. β-
Fe2O3 particles prepared at 350 had granular shapes with the small particle size of about 50 to 100 nm. However, β-Fe2O3 particles prepared at 500 had large cubic shapes and their size was about 1µm. Particle shapes including their seizes were dramatically changed between 350 and 500 . This phenomenon was caused by the formation of the liquid phase. The formation of the liquid phase at 490 was confirmed by the TG/DTA analysis.
The temperature dependence of magnetization for β-Fe2O3 particles prepared at different heat treated temperature is shown in Fig. 4. The magnetization curves were obtained under the field cooling process at 0.2 kOe. Both samples showed the characteristic curves for antiferromagnetic materials. The β-Fe2O3 particles prepared at 500 had the TN=119 K. While the ones prepared at 350 had the TN=113 K. The decreased TN for the latter sample could be caused by the reduced particle size in nanometer range.
Fig. 2 XRD patterns of the mixture of NaCl and NaFe(SO4)2 with mixing ratio 4 versus 1 (molar ratio) washed with distilled water after heating at various temperature
Fig. 3 Typical SEM image of β- Fe2O3 particles formed at (a)
350 and (b) 500
Fig. 4 Temperature dependence of magnetization of (a) β-Fe2O3 formed at 350 and (b) at 500 from the mixture of NaFe(SO4)2 and NaCl under the field of 0.2 kOe
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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Finally Mössbauer spectra of β-Fe2O3 prepared at 350 are shown in Fig. 5, at various operation temperatures. The spectra above TN showed the simple paramagnetic doublet. However, below the TN, the spectra were transformed into the two sets of magnetic hyperfine patterns. The magnetic split pattern was almost identical with ref. [2] and [9]. The spectra were clearly assigned to two unequivalent Fe3+ sites (24d and 8b sites).
4. Conclusion Single phase of β-Fe2O3 was prepared by heating the mixture of NaCl and NaFe(SO4)2 at 350500 , regardless of the mixing ratio of NaCl and NaFe(SO4)2. β-Fe2O3 was formed by the following reaction of NaFe(SO4)2 with NaCl. The obtained β-Fe2O3 had different shapes and sizes depending on the heating temperatures. Below 490 , the products had small particle size of about 50 to 100 nm. While, above 490 , The large cubic particles with a size of about 1µm were formed β-Fe2O3 was antiferromagnetic. The TN of β-Fe2O3 was decreased with decreasing the particle size from 119 K to 113 K.
References [1] Bonnevic-Svendsen M 1958 Naturwissenschaften, 45, 542 [2] Ikeda Y, Takano M and Bando Y 1986 Bull. Inst. Chem. Res., Kyoto Univ., 64, 249 [3] Wiarda D, Wenzel T, Uhrmacher M and Lieb K P 1992 J. Phys.Chem. Solids, 53, 1199 [4] Zboril R, Mashlan M and Petridis D 2002 Chem. Mater., 14, 969 [5] Ben-Dor L, Fischbein E, Felner I and Kalman Z 1977 J. Electrochem.Soc., 124, 451 [6] Gonzales-Carreno T, Morales M P and Serna C J 1994 J. Mater. Sci.Lett., 13, 381 [7] Lee C W, Jung S S and Lee J S 2007 Mater. Letters, 62, 561 [8] Fujii E, Torii H, Tomozawa A, Takayama R and Hirao T 1995 J.Cryst. Growth, 151, 134 [9] Zboril R, Mashlan M, Krausova D and Pikal P 1999 Hyperfine Interact, 497, 121
Fig. 5 Mössbauer spectra of β-Fe2O3 formed at 350 at various temperatures
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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View the article online for updates and enhancements.
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This content was downloaded from IP address 187.181.54.77 on 12/10/2021 at 22:42
Formation mechanism of nano-crystalline ββββ-Fe2O3 particles with bixbyite structure and their magnetic properties
T. Danno1, H. Asaoka1, M. Nakanishi1, T. Fujii1, Y. Ikeda2, Y. Kusano3,
J. Takada1 1Department of Material Chemistry, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan 2 Institute of Chemistry Research, Kyoto University, Kyoto 611-0011, Japan 3 Department of Applied Arts and Design, Kurashiki University of Science and the Arts, Kurashiki, Okayama 712-8505, Japan
E-mail:[email protected]
Abstract. Formation mechanism of nano-crystalline β-Fe2O3 particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO4)2 to NaCl and heating treatment temperature. A single phase of β-Fe2O3 was formed regardless of the mixing ratio. The heat treatment temperature strongly affected the particle shapes and sizes. Below 490 , they had granular shape with a diameter of about 50 to 100 nm. While, above 490 , cubic particles with increased size of about 1 µm were produced. All samples were antiferromagnetic at low temperature. The Néel temperature (TN) of 119 K for the large cubic particles was decreased to 113 K for the nanoparticles.
1. Introduction β-Fe2O3 discovered by Bonnevie-Svendsenat at 1956 is one of the polymorphs of iron () oxides [1]. Ιt is known as metastable phase of iron oxides below 770 K. β-Fe2O3 has a body-centered cubic
(bixbyite) structure with a space group of Ia3. The lattice parameter is a0=9.398 [2]. The cubic unit contains 24 Fe3+ ions with C2 symmetry (d site) and 8 ions with C3i Symmetry (b site) [3-5]. The Néel temperature (TN) of magnetic transition was reported between 110 K and 119 K [2,3]. β-Fe2O3 transforms into α-Fe2O3 above 770 K [3,5].
There are several reports about the preparation of β-Fe2O3 [1-9]. However there are only few reports obtaining the single phase β-Fe2O3 [2] and concerning about the magnetic properties of β- Fe2O3 [2,3]. According to ref. [2], β-Fe2O3 was made from the mixtures of Fe2(SO4)3 and NaCl heated at about 500 . However, the formation mechanism and magnetic properties of β-Fe2O3 were still unrevealed. We have already succeeded to prepare the single phase of β-Fe2O3 from the mixture of NaFe(SO4)2 and NaCl . We should mention here that NaFe(SO4)2 was one of the intermediate products in the way of the direct reaction between Fe2(SO4)3 and NaCl. In this paper, we investigate the formation mechanism of β-Fe2O3 by controlling the mixing ratio of NaFe(SO4)2 and NaCl, and also by
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
c© 2010 IOP Publishing Ltd 1
controlling heating conditions. The effects of preparation condition on magnetism for obtained samples will be investigated.
2. Experimental The starting materials were the reagent grade of NaCl, Na2SO4 and Fe2(SO4)3. NaFe(SO4)2 was obtained by evaporating the aqueous solution containing Na2SO4 and Fe2(SO4)3. After that, various amount of NaCl was added to NaFe(SO4)2 and thoroughly mixed in an alumina mortar. The mixtures put in an alumina crucible were heated in the air under the various temperatures for 1 hour. After cooling down to room temperature, the reaction products were dispersed in distilled water and filtered. Phase identification was done by X-ray diffraction (XRD) method in a Rigaku Rint-2000 using CuKα radiation. Morphological properties such as article shapes and sizes were observed by field-emission scanning electron microscopy (FE-SEM, HITACHI S-4300). Magnetic properties of them were characterized by SQUID magnetometer (Quantum Design MPMS2) and Mössbauer spectroscopy.
3. Results and Discussion When a mixture of NaCl and NaFe(SO4)2 was heated in the air above 550 , the final product always contained α-Fe2O3 . Therefore we focused here the heating temperature below 500 . From the differential thermogravimetrical analysis (TG/DTA), the mixture of NaCl and NaFe(SO4)2 was indicated to start reaction at about 320 . This temperature was much lower than the corresponding reaction temperature (about 400 ) of Fe2(SO4)3 with NaCl [2].
Fig. 1 shows XRD patterns of the obtained samples with various mixing ratios after the heat treatment at 500 and washed with the distilled water. The XRD results clearly indicated that the single phase of β-Fe2O3 was produced as a final product regardless of the mixing ratio of NaFe(SO4)2 to NaCl.
Fig. 2 shows XRD patterns of the heat treated samples at difference temperature. The mixing ratio
of NaCl and NaFe(SO4)2 was fixed to 4:1 (molar ratio). Single phase of β-Fe2O3 was obtained at both temperatures. Formation of β-Fe2O3 at 350 is considerably lower than the reaction temperature reported in literatures using Fe2(SO4)3 and NaCl as the starting materials [2,9].
Fig. 1 Typical XRD patterns of the mixture with various ratios heated at 500 and washing with the distilled water
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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Fig. 3 shows the SEM images of β-Fe2O3 particles prepared at 350 and 500 , respectively. β-
Fe2O3 particles prepared at 350 had granular shapes with the small particle size of about 50 to 100 nm. However, β-Fe2O3 particles prepared at 500 had large cubic shapes and their size was about 1µm. Particle shapes including their seizes were dramatically changed between 350 and 500 . This phenomenon was caused by the formation of the liquid phase. The formation of the liquid phase at 490 was confirmed by the TG/DTA analysis.
The temperature dependence of magnetization for β-Fe2O3 particles prepared at different heat treated temperature is shown in Fig. 4. The magnetization curves were obtained under the field cooling process at 0.2 kOe. Both samples showed the characteristic curves for antiferromagnetic materials. The β-Fe2O3 particles prepared at 500 had the TN=119 K. While the ones prepared at 350 had the TN=113 K. The decreased TN for the latter sample could be caused by the reduced particle size in nanometer range.
Fig. 2 XRD patterns of the mixture of NaCl and NaFe(SO4)2 with mixing ratio 4 versus 1 (molar ratio) washed with distilled water after heating at various temperature
Fig. 3 Typical SEM image of β- Fe2O3 particles formed at (a)
350 and (b) 500
Fig. 4 Temperature dependence of magnetization of (a) β-Fe2O3 formed at 350 and (b) at 500 from the mixture of NaFe(SO4)2 and NaCl under the field of 0.2 kOe
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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Finally Mössbauer spectra of β-Fe2O3 prepared at 350 are shown in Fig. 5, at various operation temperatures. The spectra above TN showed the simple paramagnetic doublet. However, below the TN, the spectra were transformed into the two sets of magnetic hyperfine patterns. The magnetic split pattern was almost identical with ref. [2] and [9]. The spectra were clearly assigned to two unequivalent Fe3+ sites (24d and 8b sites).
4. Conclusion Single phase of β-Fe2O3 was prepared by heating the mixture of NaCl and NaFe(SO4)2 at 350500 , regardless of the mixing ratio of NaCl and NaFe(SO4)2. β-Fe2O3 was formed by the following reaction of NaFe(SO4)2 with NaCl. The obtained β-Fe2O3 had different shapes and sizes depending on the heating temperatures. Below 490 , the products had small particle size of about 50 to 100 nm. While, above 490 , The large cubic particles with a size of about 1µm were formed β-Fe2O3 was antiferromagnetic. The TN of β-Fe2O3 was decreased with decreasing the particle size from 119 K to 113 K.
References [1] Bonnevic-Svendsen M 1958 Naturwissenschaften, 45, 542 [2] Ikeda Y, Takano M and Bando Y 1986 Bull. Inst. Chem. Res., Kyoto Univ., 64, 249 [3] Wiarda D, Wenzel T, Uhrmacher M and Lieb K P 1992 J. Phys.Chem. Solids, 53, 1199 [4] Zboril R, Mashlan M and Petridis D 2002 Chem. Mater., 14, 969 [5] Ben-Dor L, Fischbein E, Felner I and Kalman Z 1977 J. Electrochem.Soc., 124, 451 [6] Gonzales-Carreno T, Morales M P and Serna C J 1994 J. Mater. Sci.Lett., 13, 381 [7] Lee C W, Jung S S and Lee J S 2007 Mater. Letters, 62, 561 [8] Fujii E, Torii H, Tomozawa A, Takayama R and Hirao T 1995 J.Cryst. Growth, 151, 134 [9] Zboril R, Mashlan M, Krausova D and Pikal P 1999 Hyperfine Interact, 497, 121
Fig. 5 Mössbauer spectra of β-Fe2O3 formed at 350 at various temperatures
International Conference on Magnetism (ICM 2009) IOP Publishing Journal of Physics: Conference Series 200 (2010) 082003 doi:10.1088/1742-6596/200/8/082003
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