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Preparation and characterization of spherical yttrium iron garnet via coprecipitation
Journal of Magnetism and Magnetic Materials 226}230 (2001) 1421}1423
Preparation and characterization of spherical yttrium iron garnet via coprecipitation M. Jafelicci Jr.*, R.H.M. Godoi Chemistry Institute, UNESP, SaJ o Paulo State University, Rua Prof. Francisco Degni, s/no, P.O. Box 355, 14801-970 Araraquara-SP, Brazil
Abstract The purpose of this work is to obtain spherical particles yttrium iron garnet (YIG) by coprecipitation technique. The spherical particles were obtained from either nitrate or chloride salt solutions by controlling the precipitation medium. Di!erent agents of dispersion such as PVP and ammonium iron sulfate were used to optimize the shape and size of YIG. Samples were characterized by X-ray di!raction, scanning electron microscopy and vibrating sample magnetometry. The results show that the samples phase transition takes place at 8503C (orthorhombic phase) and at 12003C (cubic phase). Spherical shape particles, with diameter of around 0.5 m, present magnetization values close to the bulk value (26 emu g\). 2001 Elsevier Science B.V. All rights reserved. Keywords: YIG; Coprecipitations; Colloidal particles; Spherical yttrium iron garnet
Materials having the garnet structure have received a great deal to attention in laser, microwave devices and ultrasonic device "elds. A variety of processing techniques has been investigated to form single-phase YIG powders [1], including coprecipitation, hydrolysis of metal alkoxides and amorphous citrate gel. The coprecipitation method [2}4] was used to control the process of precipitation because when particles are formed they may change the nature of the solution. A better control can be obtained if the anion species, and hence precipitate, are generated simultaneously and uniformly throughout the solution. The magnetic properties of a given particle depend on a sensitive manner on size and shape. Speci"cally, the particle shape is important to control the characteristics of the magnetic anisotropy. In this paper we present an alternative method to obtain spherical YIG particles by using the coprecipitation technique from controlled hydrolysis of metal salts. Yttrium chloride 99.9%, iron chloride 97%, yttrium nitrate 99.9%, iron nitrate 99%, urea p.a, ammonium hydroxide, ammonium iron (III) sulfate 99% and * Corresponding author. Tel.: #55-16-2016651; fax: #5516-222-7932. E-mail address: [email protected] (M. Jafelicci Jr. ).
poly(vinylpyrrolidone) (PVP) were used as supplied. YIG amorphous particles were obtained by hydrolysis of metal chloride or nitrate solutions. The starting solution is a mixture of iron chloride and yttrium chloride in chloridic acid 0.01 mol l\ or a mixture of iron and yttrium nitrates in adequate proportions. These solutions were mixed, according to the ratio of Fe to Y equal to 5 : 3, and preheated up to 903C. Afterwards, urea or ammonia was added in di!erent concentrations in order to increase pH and improve the hydrolysis process. In some cases, it was added 1 wt% of poly(vinylpyrrolidone) [PVP] and/or 50 wt% of ammonium iron (III) sulfate to avoid aggregation [5]. The powder was then dried in a desiccator under vacuum and "red in air at 11003C for an hour. Table 1 describes the precipitation conditions of yttrium iron garnet. Samples were obtained with polycrystalline structure, spherical shape and appropriated magnetic properties. These samples were characterized by X-ray powder di!raction, scanning electron microscopy (JEOL-T300-BEIS) and vibrating sample magnetometer (VSM4500 Princeton Applied Research). X-ray patterns were obtained with a Siemens D5000 di!ractometer. High-temperature powder di!raction patterns were obtained by using the HTK (high-temperature camera) assembled on a Siemens -goniometer operating at
0304-8853/01/$ - see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 9 9 6 - 3
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M. Jafelicci Jr., R.H.M. Godoi / Journal of Magnetism and Magnetic Materials 226}230 (2001) 1421}1423
Table 1 Experimental conditions for YIG samples preparations. The samples P and N were obtained from chloride or nitrate anion solutions, respectively Samples
Agent (mol l\)
PVP (wt%)
NH Fe(SO ) (wt%)
P16 P3 P24 N3 N4
Urea Urea Urea Urea Urea
(0.5) (1.0) (0.5) (0.5) (0.5)
* * 1.0 * 1.0
* * 50% 50% 50%
N5 N7 N8
Urea (0.5) NH (0.5) NH (0.5)
* * 1.0
* 50% 50%
Fig. 2. Hysteresis loops of samples N4 and P24 recorded at room temperature.
Table 2 Magnetic measurements for YIG samples. All samples were heated at 11003C for 1 h
Fig. 1. XRD patterns of Fe Y O compound, sample P16 heated from 7003C to 12003C.
temperatures ranging from 253C up to 12003C with a position-sensitive detector (PSD-50 M). Several sets of X-ray powder di!raction data at various temperatures were collected for structural analysis. Fig. 1 shows the X-ray di!raction patterns of sample P16 obtained by increasing the temperature from 700 to 12003C. Through Fig. 1, the evolution of the crystalline phase was investigated in function of heating temperature. The X-ray di!raction pattern of sample P16 presents peaks characteristic of cubic YIG that was con"rmed by the index card JCPDS-ICDD, number 43-0507. The temperatures of phase transitions are identi"ed beginning at 7003C, non-crystalline-orthorhombic ferrite and at 10003C orthorhombic-cubic ferrite for the sample P16. Fig. 2 shows hysteresis loops recorded at room temperature for the P24 and N4 samples. No change on the magnetization value with the addition of PVP and
Sample
M (emu g\)
M (emu g\)
H (Oe)
P3 P16 P24 N4 N5 N7
24.70 27.01 25.12 25.22 17.13 19.22
10.00 13.18 8.21 10.60 7.85 9.94
86 78 76 108 98 101
NH Fe(SO ) is observed. Table 2 shows the values of magnetization M , remanent magnetization M and co ercive "eld H , measured at 2.5 kOe for the crystallized samples heated at 11003C. It must be emphasized that the crystalline samples show their magnetization M next to the bulk [2,6,7] value (26 emu g\), as observed in Fig. 2. This discrepancy might be due to the existence of amorphous impurities undetected by XRD or perhaps to small particle size. These samples exhibit appropriated values of remanent magnetization M and coercive "eld H , being these properties in#uenced by the particle size [2]. Scanning electron microscopy results in Fig. 3 show spherical particles of yttrium iron garnet obtained by coprecipitation method. Figs. 3a and b have demonstrated that the morphology of yttrium iron garnet particles can be in#uenced by the addition of PVP and/or NH Fe(SO ) . These stabili zation agents showed a satisfactory behavior in the dispersion of ethanol and they did not a!ect the spherical shape. The addition of PVP and or NH Fe(SO ) in speci"c amounts leads generally to a smaller particles
M. Jafelicci Jr., R.H.M. Godoi / Journal of Magnetism and Magnetic Materials 226}230 (2001) 1421}1423
Fig. 3. SEM micrograph of YIG dispersed in ethanol: a * sample N5, [Fe]"1;10\ mol l\, [Urea]"0.5 mol l\, b * sample N3, [Fe]"1;10\ mol l\, [Urea]"0.5 mol l\, 50% NH Fe(SO ) .
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scanning electron microscopy. Phase transition temperature from amorphous to crystalline YIG is around 8503C and the transition from orthorhombic to cubic phases occurs at 11003C. YIG exhibits saturation magnetization values at room temperature from 17 to 27 emu g\. Depending on the chemistry route used to obtain the YIG, particles have a di!erent size and show changes in the magnetic behavior. So it seems that YIG ceramics produced by coprecipitation, as well as those elaborated by solid-state reaction, are suitable for microwave applications. We acknowledge the "nancial support from FAPESP.
and more dispersed due to the stabilization properties. Pure YIG particle size is around 1 m, and when precipitated in presence of NH Fe(SO ) or PVP and NH Fe(SO ) is around 0.5 m. The PVP was only used to improve the dispersability. In this work, the in#uences of chloride and nitrate anions on the spherical shape have not been observed. The results show that the rigorous control of the production parameters permits the preparation, by using the simple method of coprecipitation, of magnetic ceramics processing satisfactory characteristics. Speci"cally, spherical yttrium iron garnet was obtained by coprecipitation with micrometric scales size. The e!ects of stabilization agents were not observed on shape of YIG by
References [1] M.H. Han, Y.S. Ahn, J. Mater. Sci. 31 (1996) 4233. [2] P. Vaqueiro, J. Rivas, A.L. Quintela, J. Mater. Chem. 7 (3) (1997) 501. [3] R.H.M. Godoi, M. Jafelicci Jr., R.F.C. Marques, L.C. Varanda, R.C. Lima, QumH m. Nova 22 (1999) 6. [4] P. Grosseau, A. Bachiorrini, B. Guilhot, Powder Technol. 93 (1997) 247. [5] E. Matijevic, W.P. Hsu, G. Wang, Colloids Surf. 61 (1991) 255. [6] C.D. Veitch, J. Mater. Sci. 26 (1991) 6527. [7] S. Taketomi, K. Kawasaki, Y. Osaki. Y. J. Am. Ceram. Soc. 77 (1994) 1787.
Preparation and characterization of spherical yttrium iron garnet via coprecipitation M. Jafelicci Jr.*, R.H.M. Godoi Chemistry Institute, UNESP, SaJ o Paulo State University, Rua Prof. Francisco Degni, s/no, P.O. Box 355, 14801-970 Araraquara-SP, Brazil
Abstract The purpose of this work is to obtain spherical particles yttrium iron garnet (YIG) by coprecipitation technique. The spherical particles were obtained from either nitrate or chloride salt solutions by controlling the precipitation medium. Di!erent agents of dispersion such as PVP and ammonium iron sulfate were used to optimize the shape and size of YIG. Samples were characterized by X-ray di!raction, scanning electron microscopy and vibrating sample magnetometry. The results show that the samples phase transition takes place at 8503C (orthorhombic phase) and at 12003C (cubic phase). Spherical shape particles, with diameter of around 0.5 m, present magnetization values close to the bulk value (26 emu g\). 2001 Elsevier Science B.V. All rights reserved. Keywords: YIG; Coprecipitations; Colloidal particles; Spherical yttrium iron garnet
Materials having the garnet structure have received a great deal to attention in laser, microwave devices and ultrasonic device "elds. A variety of processing techniques has been investigated to form single-phase YIG powders [1], including coprecipitation, hydrolysis of metal alkoxides and amorphous citrate gel. The coprecipitation method [2}4] was used to control the process of precipitation because when particles are formed they may change the nature of the solution. A better control can be obtained if the anion species, and hence precipitate, are generated simultaneously and uniformly throughout the solution. The magnetic properties of a given particle depend on a sensitive manner on size and shape. Speci"cally, the particle shape is important to control the characteristics of the magnetic anisotropy. In this paper we present an alternative method to obtain spherical YIG particles by using the coprecipitation technique from controlled hydrolysis of metal salts. Yttrium chloride 99.9%, iron chloride 97%, yttrium nitrate 99.9%, iron nitrate 99%, urea p.a, ammonium hydroxide, ammonium iron (III) sulfate 99% and * Corresponding author. Tel.: #55-16-2016651; fax: #5516-222-7932. E-mail address: [email protected] (M. Jafelicci Jr. ).
poly(vinylpyrrolidone) (PVP) were used as supplied. YIG amorphous particles were obtained by hydrolysis of metal chloride or nitrate solutions. The starting solution is a mixture of iron chloride and yttrium chloride in chloridic acid 0.01 mol l\ or a mixture of iron and yttrium nitrates in adequate proportions. These solutions were mixed, according to the ratio of Fe to Y equal to 5 : 3, and preheated up to 903C. Afterwards, urea or ammonia was added in di!erent concentrations in order to increase pH and improve the hydrolysis process. In some cases, it was added 1 wt% of poly(vinylpyrrolidone) [PVP] and/or 50 wt% of ammonium iron (III) sulfate to avoid aggregation [5]. The powder was then dried in a desiccator under vacuum and "red in air at 11003C for an hour. Table 1 describes the precipitation conditions of yttrium iron garnet. Samples were obtained with polycrystalline structure, spherical shape and appropriated magnetic properties. These samples were characterized by X-ray powder di!raction, scanning electron microscopy (JEOL-T300-BEIS) and vibrating sample magnetometer (VSM4500 Princeton Applied Research). X-ray patterns were obtained with a Siemens D5000 di!ractometer. High-temperature powder di!raction patterns were obtained by using the HTK (high-temperature camera) assembled on a Siemens -goniometer operating at
0304-8853/01/$ - see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 9 9 6 - 3
1422
M. Jafelicci Jr., R.H.M. Godoi / Journal of Magnetism and Magnetic Materials 226}230 (2001) 1421}1423
Table 1 Experimental conditions for YIG samples preparations. The samples P and N were obtained from chloride or nitrate anion solutions, respectively Samples
Agent (mol l\)
PVP (wt%)
NH Fe(SO ) (wt%)
P16 P3 P24 N3 N4
Urea Urea Urea Urea Urea
(0.5) (1.0) (0.5) (0.5) (0.5)
* * 1.0 * 1.0
* * 50% 50% 50%
N5 N7 N8
Urea (0.5) NH (0.5) NH (0.5)
* * 1.0
* 50% 50%
Fig. 2. Hysteresis loops of samples N4 and P24 recorded at room temperature.
Table 2 Magnetic measurements for YIG samples. All samples were heated at 11003C for 1 h
Fig. 1. XRD patterns of Fe Y O compound, sample P16 heated from 7003C to 12003C.
temperatures ranging from 253C up to 12003C with a position-sensitive detector (PSD-50 M). Several sets of X-ray powder di!raction data at various temperatures were collected for structural analysis. Fig. 1 shows the X-ray di!raction patterns of sample P16 obtained by increasing the temperature from 700 to 12003C. Through Fig. 1, the evolution of the crystalline phase was investigated in function of heating temperature. The X-ray di!raction pattern of sample P16 presents peaks characteristic of cubic YIG that was con"rmed by the index card JCPDS-ICDD, number 43-0507. The temperatures of phase transitions are identi"ed beginning at 7003C, non-crystalline-orthorhombic ferrite and at 10003C orthorhombic-cubic ferrite for the sample P16. Fig. 2 shows hysteresis loops recorded at room temperature for the P24 and N4 samples. No change on the magnetization value with the addition of PVP and
Sample
M (emu g\)
M (emu g\)
H (Oe)
P3 P16 P24 N4 N5 N7
24.70 27.01 25.12 25.22 17.13 19.22
10.00 13.18 8.21 10.60 7.85 9.94
86 78 76 108 98 101
NH Fe(SO ) is observed. Table 2 shows the values of magnetization M , remanent magnetization M and co ercive "eld H , measured at 2.5 kOe for the crystallized samples heated at 11003C. It must be emphasized that the crystalline samples show their magnetization M next to the bulk [2,6,7] value (26 emu g\), as observed in Fig. 2. This discrepancy might be due to the existence of amorphous impurities undetected by XRD or perhaps to small particle size. These samples exhibit appropriated values of remanent magnetization M and coercive "eld H , being these properties in#uenced by the particle size [2]. Scanning electron microscopy results in Fig. 3 show spherical particles of yttrium iron garnet obtained by coprecipitation method. Figs. 3a and b have demonstrated that the morphology of yttrium iron garnet particles can be in#uenced by the addition of PVP and/or NH Fe(SO ) . These stabili zation agents showed a satisfactory behavior in the dispersion of ethanol and they did not a!ect the spherical shape. The addition of PVP and or NH Fe(SO ) in speci"c amounts leads generally to a smaller particles
M. Jafelicci Jr., R.H.M. Godoi / Journal of Magnetism and Magnetic Materials 226}230 (2001) 1421}1423
Fig. 3. SEM micrograph of YIG dispersed in ethanol: a * sample N5, [Fe]"1;10\ mol l\, [Urea]"0.5 mol l\, b * sample N3, [Fe]"1;10\ mol l\, [Urea]"0.5 mol l\, 50% NH Fe(SO ) .
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scanning electron microscopy. Phase transition temperature from amorphous to crystalline YIG is around 8503C and the transition from orthorhombic to cubic phases occurs at 11003C. YIG exhibits saturation magnetization values at room temperature from 17 to 27 emu g\. Depending on the chemistry route used to obtain the YIG, particles have a di!erent size and show changes in the magnetic behavior. So it seems that YIG ceramics produced by coprecipitation, as well as those elaborated by solid-state reaction, are suitable for microwave applications. We acknowledge the "nancial support from FAPESP.
and more dispersed due to the stabilization properties. Pure YIG particle size is around 1 m, and when precipitated in presence of NH Fe(SO ) or PVP and NH Fe(SO ) is around 0.5 m. The PVP was only used to improve the dispersability. In this work, the in#uences of chloride and nitrate anions on the spherical shape have not been observed. The results show that the rigorous control of the production parameters permits the preparation, by using the simple method of coprecipitation, of magnetic ceramics processing satisfactory characteristics. Speci"cally, spherical yttrium iron garnet was obtained by coprecipitation with micrometric scales size. The e!ects of stabilization agents were not observed on shape of YIG by
References [1] M.H. Han, Y.S. Ahn, J. Mater. Sci. 31 (1996) 4233. [2] P. Vaqueiro, J. Rivas, A.L. Quintela, J. Mater. Chem. 7 (3) (1997) 501. [3] R.H.M. Godoi, M. Jafelicci Jr., R.F.C. Marques, L.C. Varanda, R.C. Lima, QumH m. Nova 22 (1999) 6. [4] P. Grosseau, A. Bachiorrini, B. Guilhot, Powder Technol. 93 (1997) 247. [5] E. Matijevic, W.P. Hsu, G. Wang, Colloids Surf. 61 (1991) 255. [6] C.D. Veitch, J. Mater. Sci. 26 (1991) 6527. [7] S. Taketomi, K. Kawasaki, Y. Osaki. Y. J. Am. Ceram. Soc. 77 (1994) 1787.