1. Art and Diseño

Author's Accepted Manuscript
Y3Fe5O12 nanoparticulate garnet ferrites:
Comprehensive study on the synthesis and
characterization fabricated by various routes
Majid Niaz Akhtar, Muhammad Azhar Khan,
Mukhtar Ahmad, G. Murtaza, R. Raza, S.F.
Shaukat, M.H. Asif, Nadeem Nasir, G. Abbas,
M.S. Nazir, M.R. Raza
www.elsevier.com/locate/jmmm
PII:
DOI:
Reference:
S0304-8853(14)00519-8
http://dx.doi.org/10.1016/j.jmmm.2014.06.004
MAGMA59124
To appear in:
Journal of Magnetism and Magnetic Materials
Received date: 27 January 2014
Revised date: 22 May 2014
Accepted date: 1 June 2014
Cite this article as: Majid Niaz Akhtar, Muhammad Azhar Khan, Mukhtar
Ahmad, G. Murtaza, R. Raza, S.F. Shaukat, M.H. Asif, Nadeem Nasir, G. Abbas,
M.S. Nazir, M.R. Raza, Y3Fe5O12 nanoparticulate garnet ferrites: Comprehensive study on the synthesis and characterization fabricated by various routes,
Journal of Magnetism and Magnetic Materials, http://dx.doi.org/10.1016/j.
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Y3Fe5O12 nanoparticulate garnet ferrites: Comprehensive study on the synthesis and
characterization fabricated by various routes
Majid Niaz Akhtara, h, *, Muhammad Azhar Khanb, Mukhtar Ahmadc, G. Murtazad, R.
Razaa, S. F. Shaukata, M. H. Asifa, Nadeem Nasire, G. Abbasf, M. S. Nazirg, M. R.
Razah
a
Department of Physics, COMSATS Institute of Information Technology, Lahore, 54000,
Pakistan.
b
Department of Physics, The Islamia University of Bahawalpur 63100, Pakistan
c
Department of Physics, Bahauddin Zakariya University, Multan 60800, Pakistan
d
Centre for Advanced Studies in Physics, G.C. University, Lahore, Pakistan.
e
Fundamental and Applied Sciences Department, National Textile University, Faisalabad,
Pakistan.
f
Department of Physics, COMSATS Institute of Information Technology, Islamabad,
Pakistan.
g
Department of Chemical Engineering, COMSATS Institute of Information Technology,
Lahore, 54000, Pakistan.
h
Department of Mechanical and Materials Engineering, Faculty of Engineering and Built
Environment, Universiti Kebangsaan Malaysia, 43600 Bangi,Selangor, Malaysia.
Corresponding author: [email protected]
ABSTRACT
The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified
conventional mixed oxide (MCMO) on the structure, morphology and magnetic properties
of the (Y3Fe5O12) garnet ferrites have been studied in the present work. The samples of
Y3Fe5O12 were sintered at 950 °C and 1150 °C (by SG and SC methods). For MCMO
route the sintering was done at 1350 °C for 6 h. Synthesized samples prepared by various
routes were investigated using X-ray diffraction (XRD) analysis, Field emission scanning
electron microscopy (FESEM), Impedance network analyzer and transmission electron
microscopy (TEM). The structural analysis reveals that the samples are of single phase
structure and shows variations in the particle sizes and cells volumes, prepared by various
routes. FESEM and TEM images depict that grain size increases with the increase of
sintering temperature from 40 to 100 nm. Dielectric measurements reveal that garnet ferrite
synthesized by sol gel method has high initial permeability (60.22) and low magnetic loss
(0.0004) as compared to other garnet ferrite samples, which were synthesized by self
combustion and MCMO methods.
The M-H loops exhibit very low coercivity which
enables the use of these materials in relays and switching devices fabrications. Thus, the
garnet nanoferrites with low magnetic loss prepared by different methods may open new
horizon for electronic industry for their use in high frequency applications.
Keywords: X-ray diffraction; Transmission electron microscopy; Initial permeability; Qfactor; Vibrating sample magnetometer.
1. Introduction
Garnets have been extensively studied as they are an important class of ferrimagnetic
materials and are promising in wide range of high frequency applications. Yttrium iron
garnet (Y3Fe5O12) is a well known garnet ferrite and has attracted considerable attention due
to its technological importance in various applications such as isolators, circulators, high
quality filters, phase shifters and many electronics magnetic optical devices [1]. Garnet
ferrites (A3B5O12) exhibit fascinating and unique electromagnetic, magneto-optical
mechanical and thermal properties [2]. In the crystal structure, garnet ferrites have three
crystallographic lattice (a, b and c) sites. It has been found that among three lattice sites
24Fe3+ ions occupy tetrahedral sites, 16Fe3+ ions occupy octahedral sites and 24R3+ ions
goes on the dodecahedral sites, where as oxygen ions are distributed to the interstitial sites
[3]. Yttrium iron garnet (Y3Fe5O12) is a versatile ceramic material which has high melting
point, large resistivity, better electromagnetic properties, high thermal stability, low thermal
expansion, better chemical stability and high thermal conductivity [4]. Also, yttrium iron
garnet has a large Faraday rotation, high initial permeability, high saturation magnetization
and strong coercive force.
The properties of garnet ferrites strongly depend on the phase formation, microstructure
fabrication techniques and sintering temperature [5]. Y3Fe5O12 used in industry for the
fabrication of different electronic devices involves the milling of oxides of yttrium (Y2O3)
and iron (Fe2O3). These oxides are calcined and then sintered at high temperatures to get
required characteristics of the garnet ferrite. It has been found that during milling of oxide
materials, existence of intermediate phases and impurities are produced which affect the
properties of garnets [6, 7]. The final sintering has been usually carried out at high
temperatures (>1450oC), due to which the final product has larger grain size (micrometer)
with less homogeneity. It has also been found that properties of any ferrite material depend
on the shape, size and morphology of the synthesized samples [8].
Therefore, the attention is being paid to synthesize garnet ferrites by various techniques in
order to have smaller grain size, better morphology, low sintering temperature and
homogeneous grain size distribution. Currently, garnet ferrites in the nano scale regime are
of much interest due to their versatile electromagnetic properties [9, 10]. Non-conventional
methods (chemical methods) such as co-precipitation [10], hydrothermal precipitation [11],
auto combustion [12], glass crystallization [13], mechanical alloying [14], sol-gel synthesis
[15, 16] and self combustion [17] are being used to synthesize the nanoparticles of garnet
ferrites. Yttrium iron garnet (YIG) prepared by conventional solid state reaction method
resulted secondary phases such as hematite Fe2O3, magnetite (Fe3O4),
YFeO3 and YFe2O4. However, YIG synthesized by non conventional
methods
produce
temperature.
The
single
phase
formation
of
structure
at
low
secondary
phases
sintering
other
than
garnet structure, deteriorate the performance of YIG ferrite
in many applications.
Mechanochemical (MCM) method has been employed to synthesize yttrium iron garnet
(Y3Fe5O12). Garnet ferrite powders annealed at 900 oC to obtain the single phase structure
from orthoferrite to YIG. Magnetic characterizations showed highest saturation
magnetization for YIG ferrite whereas the lowest for orthoferrite. It has also been observed
that saturation magnetization showed intermediate values of the mixtures of YIG and
orthoferrite phases [18]. In the earlier study, it has been observed that the crystallization
temperature can be reduced by using sol gel method as compared to the other methods [19].
The influence of particle size on the properties (structural and magnetic) of the yttrium iron
garnet nanoparticles synthesized by sol-gel method has been reported. Results reveal that as
the particle size decreases, saturation magnetization also decreases. Single domain has been
reported at critical diameter of Ds =190 nm at which coercivity is maximum. While, super
paramagnetic behavior has been found at Dp= 35 nm [20].
Many reports have been presented about the structural and magnetic evaluation of yttrium
iron garnets. To the best of our knowledge microstructural, static and dynamic magnetic
properties of nanoparticulate YIG synthesized by various routes are rarely reported. The
properties of YIG nanoparticles are greatly influenced by the preparation methods and
strongly dependent on the phase, structure and grain size of the prepared garnet ferrites.
Therefore, in the present study different methods have been adopted for the preparation of
garnet ferrite nanoparticles [21-22]. Nanoparticulates YIG have been synthesized by sol-gel,
self combustion and MCMO methods. The fabricated samples were characterized by
structural, and morphological point of view, whereas, the static and dynamic magnetic
characterizations were also evaluated by measuring the Ls-Q values of the toroidal cores and
MH loops of the magnetic samples respectively. The aim of the present work is to fabricate
nanoparticles of YIG and to obtain low loss YIG with optimized properties which make
these nano materials suitable for switching and high frequency devices fabrications.
2. Materials and Methods
2.1 Materials
The raw materials, iron nitrate (Fe(NO3)3.9H2O) and yttrium nitrate (Y(NO3)3.6H2O),
having 99.99% purity were used as starting materials. All metal nitrates with stoichiometric
ratios were dissolved in an aqueous solution of 160 ml of citric acid (C6H8O7.H2O). Citric
acid was dissolved to get homogenous solution whereas a molar ratio of metal ions to citric
acid was kept as 1:1.
2.2 Preparation of Samples
2.2.1 Preparation of Y3Fe5O12 by sol gel method
Yttrium nitrate (Y(NO3)3.6H2O, 99.99%) and iron nitrate (Fe(NO3)3.9H2O, 99.99%) for the
synthesis of yttrium iron garnet (Y3Fe5O12) were dissolved in the aqueous solution of 160 ml
of citric acid (C6H8O7.H2O). The solution was stirred at 300 rpm for 7 days and was allowed
to form gel on the hot plate stirrer with gradual heating. The temperature was increased after
every 20 min until 80°C. The samples in gel form were dried in an oven at 110°C for
24hours. The dried powder was grounded for 6 hours and then sintered at 950°C and
1150°C for 4hours in air furnace.
2.2.2 Preparation of Y3Fe5O12 by self-combustion method
The solution of yttrium iron garnet (Y3Fe5O12) was stirred at 300 rpm for 7 days and was
combusted on the hot plate stirrer with a gradual heating after 40 min until the temperature
reached 110°C. The combusted material was dried in the oven at 110°C for 24 hours and
dried powder was ground for 6 hours. The powder was sintered at 950°C and 1150°C for 4
hours. Fig. 1 (a) shows the flow diagram for the synthesis of nanocrystalline YIG ferrite
powder by sol gel method and self combustion method.
2.2.3 Preparation of Y3Fe5O12 by MCMO method
The iron oxide Fe2O3 (99.99%) and yttrium oxide Y2O3 (99.99%) were used as starting
materials for the synthesis of Y3Fe5O12. Since Fe2O3 and Y2O3 are insoluble in water,
therefore they were dissolved in HNO3 to make them soluble in water. These solutions were
then dissolved in the aqueous solution of 160 ml of citric acid, C6H8O7.H2O. The solution
was stirred at 300 rpm for 7 days and then was combusted on the hot plate stirrer with a
gradual heating until the temperature was 110°C. The combusted material was dried at
110°C in the oven for 2 days and grounded for 4 hours. Then, the powder was sintered at
950°C, 1150°C and 1350°C respectively for 6 hours. Fig. 1 (b) shows the flow diagram for
the synthesis of nanocrystalline YIG ferrite powder by sol gel method and self combustion
method.
2.3 Fabrication of Magnetic Toroids
Y3Fe5O12 nanoparticles sintered at 950°C, 1150°C and 1350°C prepared by sol-gel and self
combustion methods were moulded to a toroidal shape by using an auto pellet hydraulic
press at 50 kN pressure. Zinc stearate (1%) which acted as a lubricant and polyvinyl alcohol
(PVA) (1%) which acted as a binder were used in nanoparticles of Y3Fe5O12 to make the
toroidal shape. The binder and lubricant were evaporated at 750°C and 950°C.
2.4 Characterizations
The phase identification and crystalline structure of the prepared samples of Y3Fe5O12 by
sol-gel, self combustion and MCMO methods were investigated using X-ray diffractometer
(Bruker D8 advance) which was operated at 40 kV and at 30 mA with CuKα radiation (λ =
1.5406 Å). Field emission scanning electron microscopy (FESEM, SUPRA 55VP ZEISS)
was used to measure the shape of nanoparticles, surface morphology, grain size and
microstructure of the samples. The morphology and grain size were also examined by
transmission electron microscopy (TEM, Zeiss Libra 200FE). Magnetic properties such as
initial permeability, Q-factor, and relative loss factor of garnet samples in toroidal form
were measured by using impedance analyzer (Agilent-4294A) from 40 Hz to 110 MHz at
the room temperature. In addition, magnetic properties such as magnetic saturation (Ms),
remanence (Mr ) and coercivity were also recorded at room temperature using vibrating
sample magnetometer (VSM).
3. Results and discussion
3.1 Phase identification
X-ray diffraction patterns of samples synthesized by sol-gel, self combustion and MCMO
method are shown in Fig. 2. The hkl and observed d-values of all the XRD patterns have
been indexed with the standard JCPDS data (43-0507) for yttrium iron garnet ferrite. The
crystallite size is measured from X-ray diffraction patterns using Debye Sherrer formula
which is given by the equation 1 [23];
D
=
K λ
ω cosθ
(1)
Where,
K, Crystallite shape equal to 0.9 and varies with hkl; θ, Bragg’s angle; ω, Full width at half
maximum (FWHM); and λ, wavelength of incident radiation.
Diffraction patterns confirm that without sintering, the yttrium iron garnet shows no peaks
but when temperature rises from 950 °C to 1350 °C, sharp peaks are appeared. A clear
diffraction line with a sharp peak [4 2 0] designates high crystallinity of the Y3Fe5O12 (YIG)
and the sintered sample at 1150 °C shows a single phase YIG garnet structure. Moreover,
purity of the samples reveal that all the peaks correspond to the garnet ferrite, with no other
peaks are observed at the sintering temperature of 1150°C and 1350°C of sol gel, self
combustion and MCMO methods respectively. It also describes that single phase structure
of the garnet ferrite with good crystallinity and high degree of perfection, whereas no crystal
deformation and impurity is observed. In Fig. 2, number of peaks with higher intensity
showed that increased in sintering temperature from 950 °C to 1350 °C gives successful
opportunity to the atoms arranged themselves in the crystal lattice. All peaks have been
exactly matched with the standard (77-1888), which is in agreement with the literature [2425]. The average crystallite size of the YIG sintered samples have been calculated from the
broadening of [420] peak using the Scherer formula as given in Equation 1. The crystallite
size shows a variation from 66nm to 74nm for the YIG sintered samples prepared by self
combustion method. It has been found that Y3Fe5O12 prepared by sol-gel method shows the
single phase structure at sintering temperature of 1150 °C, while, this trend observed in the
samples at sintering temperature 1350 °C using MCMO method. The XRD results also
reveal that the crystallite sizes (D) of sintered samples at 950°C, 1150 °C and 1350 °C were
66 nm, 68 nm, 73 nm and 102 nm respectively. The crystallite size, lattice parameter and
cell volume of the YIG samples were found to be increased as the sintering temperature
increased due to the coalescence of smaller particles as indicated in Table I.
3.2 Microstructure Analysis Using FESEM and TEM
The morphological study and the dimensions of the grain size of the YIG samples were
analyzed using field emission scanning electron microscope (FESEM). FESEM micrographs
of YIG samples sintered at 950 °C, 1150 °C and 1350 °C using different synthesis methods
are shown in Figs. (3-5). From FESEM, it reveals that most of the particles are
agglomerated with each other uniformly at 950 oC. Pores in the Y3Fe5O12 sintered samples
at 950 °C, 1150 °C and 1350 °C prevent atoms to diffuse on, resulting the stable in
nanocrystalline powder, which further confirmed by XRD. Porous features after sintering of
the Y3Fe5O12 samples indicate the easy breaking of the agglomeration at higher
temperatures [26-27]. There is no agglomeration in the Y3Fe5O12 sample sintered at 1150°C,
which shows a uniform grain structure. It is confirm that changes in the particle size and
morphology of the Y3Fe5O12 samples sintered at 950 °C and 1150 °C are attributed due to
the breaking and welding of particles. The grain size of the sample also increases as the
temperature increase from 750 °C to 1150 °C. It is also observed that the grain size of the
Y3Fe5O12 prepared by the self-combustion method is smaller in size as compared to the
samples prepared by the conventional method [28]. It is due to yttrium iron ions have a
larger ionic radii (0.89 Å) than the ferrous ions (0.65 Å). Therefore, the ferrous ions go to
tetrahedral and octahedral sites, whereas yttrium ions go to the dodecahedral sites (2.40 Å)
[29]. From Fig. 4, micrographs of the most particles are different in shape and sizes from
each other and show uniformity at 1150 oC. This may attributed to the large surface area of
the YIG nanoparticles [28]. However, as the sintering temperature increases from 950 oC to
1350 oC, the particles do not agglomerate and show dispersed grains of yttrium iron garnets.
The grain sizes of the sample also increase as the sintering temperature increased from 950
o
C to 1350 oC. It has been reported that grain size depends on many factors such as sintering
temperature, porosity and grain boundary [30-31].
High resolution transmission electron microscopy was used to see the particle shape and
size of the Y3Fe5O12 prepared by various methods (Figs. 6-8). The representative
transmission electron microscopy (TEM) images of Y3Fe5O12 prepared by the sol gel, selfcombustion and MCMO method at different sintering temperatures 950 °C, 1150 °C, 1350
°C respectively are shown in Figs. 6-8. TEM micrographs revealed that the Y3Fe5O12 single
phase with good crystallinity has been achieved at the sintering temperature of 1150 °C and
1350°C. The average grain size varies between 60 nm to 110 nm of Y3Fe5O12. It can be
seen that YIG samples prepared by sol-gel method show better morphology, smaller grain
size as compared to the YIG samples prepared by other methods.
3.3 Magnetic Measurements of Y3Fe5O12 Ferrite Samples by different methods
3.3.1 Initial Permeability, Q factor and Magnetic Losses
The series values of the inductance, Ls and Q values were recorded from the lowest
frequency to the resonance frequencies from the impedance vector network analyzer
(Agilent 4294 A). Initial permeability and relative loss factor (RLF) of the yttrium iron
garnet sintered at 950 °C, 1150 °C and 1350 °C were calculated by using the network
analyzer. The initial permeability increase with an increasing frequency, whereas the
relative loss factor (RLF) decreases as the frequency increase as shown in Fig. 8. It has been
reported that the ferrite materials have higher initial permeability due to a bulk density and
large grain size [31]. Bulk density normally increases due to the pores and also raises its
rotational spin contribution which also contributes to an increase in the permeability. The
initial permeability and Q-factor of the Y3Fe5O12 sample sintered at 1150 oC show the
highest value as compared to the YIG sample sintered at 950 oC and 750 oC. The relative
loss factor shows lower values due to higher values of initial permeability and Q-values.
The initial permeability increases due to less interruption between domain walls, which may
be due to the decrease in magnetic anisotropy, internal stress and crystal anisotropy at
higher temperatures. The surface morphology, density, porosity, grain size, Fe2+ content and
single phase structure of the ferrites may affect the initial permeability. The magnetizing
effect in soft ferrites result is due to the spin domain rotation and domain wall motion. It has
also been investigated that when the cut off frequency is less than 40MHz, the grain size is
less than 5 μm, then the domain wall motion dominate and contributed to the magnetism
[32]. The Q-factor values show the cut off frequency less than 40 MHz and the grain size is
in the nanometer range. Such type of materials can be used for low frequency applications.
The relative loss factor is the ratio of the tanδ to the initial permeability. The relative loss
factor has been seen to be decreasing down to 10 MHz and after that it remained smooth.
The frequency at which the relative loss factor decreases and has a minimum value is called
the threshold frequency. The low loss factor values indicate a high purity of samples
obtained by a non conventional (wet) method [33-36].
Initial permeability and relative loss factor (RLF) of yttrium iron garnet sintered at 1150 °C
and 1350 °C were calculated using a network analyzer. The initial permeability increases
with the increasing frequency, whereas the relative loss factor (RLF) decreases as the
frequency increase as shown in Figures (9- c). The initial permeability increased due to less
interruption between domain walls, which may be due to the decrease in the magnetic
anisotropy, internal stress and crystal anisotropy at higher temperatures. The relative loss
factor is the ratio of the tanδ to the initial permeability. It has also been investigated that if
the cut off frequency is less than 40MHz and the grain size is less than 5μm, then the
domain wall motion dominates and contributes in magnetism [34]. The YIG samples
prepared by sol-gel method show highest initial permeability, largest Q-factor and low loss
factor as compared to the self combustion and MCMO method. This may be due to the
better morphology, single phase structure at low sintering temperature as compared to the
YIG samples prepared by other synthesis methods.
3.3.2 Magnetic Hysteresis Loops
Fig. 10 shows the M–H loops for all yttrium iron garnet (YIG) samples synthesized using
different routes and
loops are measured up to an applied field of 15 kOe at room
temperature. It has been observed that the width and shape of the M-H loops depends on the
synthesis method, grain size, and porosity etc, of the prepared YIG samples. From the M-H
loops, it can be estimated that the saturation magnetization (Ms) is very high whereas the
coercivity (Hc) is low in all samples of the YIG ferrite, which indicate strong magnetism.
The saturation magnetization Ms, remanence Mr and coercivity Hc for all samples is given
in Table II. The values of the saturation magnetization and remanence have been found in
the range of 0.95 to 0.10emu/g and 0.91 to 0.07emu/g respectively. Hysteresis loops of all
the YIG samples strongly associated and dependent on the sintering temperature and
synthesis method. The samples synthesized by MCMO method at 1150°C have low
saturation magnetization and remanence as compared to other samples. Furthermore, the
coercivity decreases in all samples with increasing the sintering temperature and synthesis
methods. The coercivity values decrease due to increase in the grain size as both parameters
are inversely related with each other (Hc α 1/r) [37]. The dependence of coercivity can be
explained with respect to the intrinsic and extrinsic properties of the investigated materials.
Intrinsic properties depend on the chemical composition, structure and magnetic anisotropy
field and energy whereas extrinsic properties depend on bulk characteristics (grain size and
shape, defects and porosity) of the materials. It was reported by Globus [38] that magnetic
moment reversal and magnetic domain wall motion played an important role for the increase
or decrease of the coercivity in the ferrite samples. In this study, coercivity decreases with
increasing grain size and morphology of the ferrite samples as sintering temperature
increase. This effect may be attributed due to the enhanced magnetic moment reversal,
domain wall migration and increased sintering temperature of the ferrite samples [39]. The
value of the coercivity in all the samples has been found a few hundred oersteds which show
the soft character of these garnet ferrites. In the present study Y3Fe5O12 nanoparticles
synthesized by all three routes exhibited the squareness ratio in the range ~1. Hence
the
magnetic
studies
revealed
that
these
garnet
ferrite
particles
exhibit
superparamagnetic behavior [40]. The variation of remanence (Mr), magnetization (Ms)
and coercivity (Hc) for YIG samples synthesized by different methods are also depicted in
Fig 11 (a, b). Moreover, the squareness ratio for all the samples were calculated from the
magnetic saturation and remanence values listed in Table II. The Ms and Mr values are
distinguishly varied as we increased the sintering temperature and also by changing
the method of preparation. The variation of magnetic remanence (Mr), Magnetic
saturation (Ms) and coercivity (Hc) for YIG samples synthesized by different methods are
also given in Table II. This variation may be due to the spin canting effect and breakage of
colinearity [41-42]. In the present investigations, it is suggested that the magnetic properties
of the YIG samples are mainly affected due to the synthesis method.
4. Conclusions
Single phase Y3Fe5O12 (YIG) garnet ferrites are obtained using different synthesized
methods. XRD results reveal that crystallization start at the sintering temperature of 950 °C
whereas the single phase structure of YIG samples with a major peak [420] has been
successfully developed at the sintering temperature of 1150 °C and 1350 °C. A significant
increase in the initial permeability and decrease in loss factor for the YIG samples
synthesized by sol gel methods have been observed due to increase in grain size and large
densification. The magnetic properties, such as, remanence and saturation are found to be
increase whereas coercivity decrease which is due to the contribution of the particle size,
magnetic dilution and superexchange interaction of the YIG ferrites. Consequently, the
homogenous nanostructures with high performance and very low loss of YIG synthesized
using sol gel method make these ferrites potential candidates for high frequency
applications.
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List of Tables
Table I XRD parameters for all YIG (Y3Fe5O12) samples synthesized using different routes
Table II Magnetic parameters for all YIG (Y3Fe5O12) samples synthesized using different
routes
List of Figures
Fig. 1 (a) Flow diagram for the synthesis of nanocrystalline YIG ferrite powder by sol gel
method and self combustion method (b) By MCMO (modified conventional metal oxide)
method.
Fig.2 XRD spectra of YIG prepared by MCMO , self combustion and sol gel method
sintering at 950°C, 1150°C and 1350°C
Fig.3 FESEM images of YIG sintering at (a) 1150°C and (b) 1350°C prepared by MCMO
method
Fig.4 FESEM images of YIG sintering at (a) 950°C and (b) 1150°C prepared by self
combustion method
Fig.5 FESEM images of YIG sintering at (a) 950°C and (b) 1150°C prepared by sol gel
method.
Fig.6 TEM images of YIG sintering at (a) 1150°C and (b) 1350°C prepared by MCMO
method
Fig.7 TEM images of YIG sintering at (a) 950°C and (b) 1150°C prepared by self
combustion method
Fig.8 TEM images of YIG sintering at 950°C and 1150°C prepared by sol gel method
Fig.9 Magnetic Measurements (a)Initial permeability, (b) Q factor (c)relative loss factor and
(d) log scale relative loss factor of YIG prepared by MCMO , self combustion and sol gel
method sintering at 950°C, 1150°C and 1350°C
Fig 10 M-H Loops of YIG (Y3Fe5O12) samples synthesized using different routs
Fig 11 (a) Variation of Saturation remanence (Mr), Magnetization (Ms) and (b) coercivity
(Hc) for YIG samples synthesized by different methods
Table I XRD parameters for all YIG (Y3Fe5O12) samples synthesized using different routes.
YIG samples
d- values
FWHM
Crysallite
Lattice
Crysallite
size (D)
Parameter
(D) by SEM
size
Cell Volume
(a) Å
YIG by MCMO at 1150 oC
2.761
0.211
68 nm
12.347
66 nm
1.882*10-27
YIG by self combustion at 950 oC
2.756
0.218
66nm
12.325
63nm
1.872*10-27
YIG by sol-gel at 950 oC
2.758
0.225
64 nm
12.334
60 nm
1.876*10-27
YIG by MCMO at 1350 oC
2.771
0.141
102nm
12.387
110nm
1.900*10-27
YIG by self combustion at 1150 oC
2.766
0.225
74nm
12.369
69nm
1.892*10-27
YIG by sol-gel at 1150 oC
2.767
0.196
73 nm
12.360
67 nm
1.888*10-27
Table II Magnetic parameters for all YIG (Y3Fe5O12) samples synthesized using different
routes.
Samples
Mr (emu/g)
Ms (emu/g)
Mr/Ms
Hc (Oe)
YIG by MCMO at 1150 oC
0.004
0.001
4.00
2160
YIG by self combustion at 950 oC
0.253
0.078
3.24
1978
YIG by sol gel at 950 oC
0.167
0.147
1.14
494
YIG by MCMO at 1350 oC
0.391
0.357
1.10
2.261
YIG by self combustion at 1150 oC
0.931
0.904
1.03
0.176
YIG by sol gel at 1150 oC
0.925
0.915
1.01
0.101
Highlights
•
Y3Fe5O12 garnet ferrites nanoparticles were synthesized by three different routes
•
Impact of sintering temperature on the particle size of Y3Fe5O12 was evaluated
•
The magnetic studies suggest the applications in relays and switching devices
Figure
(a)
Metal Nitrates+ Citric
acid + De-ionized water
Aqueous Solution
Sol-Gel Method
Self Combustion Method
Stirring
pH=7
Sol
Gel
Stirring solution and
heated at 80oC for sol-gel
and 110oC for self
combustion method
Stirring
Heated until
combustion
Drying
Drying
Ferrite Powder +
Toroids
Ferrite Powder +
Toroids
Sintering at different
temperatures
YIG nanoferrite
YIG nanoferrite
(b)
Y2O3+Fe2O3+
Citric acid+
Deionised water
pH=7
Aqueous solution
Stirring
Heated until
combustion
Stirring solution
and evaporation
at 110oC
Drying
Ferrite Powder
+ Toroids
Sintering
YIG nanoferrite
Fig. 1
Intensity (a.u)
o
[6 4 0]
[4 4 4]
[5 4 3]
[6 3 1]
by sol gel method at 950 C
o
by self combustion method at 950 C
o
by MCMO at 1150 C
o
by MCMO at 1350 C
o
by self combustion method at 1150 C
o
by sol gel method at 1150 C
[6 1 1]
[6 2 0]
[5 4 1]
[4 4 0]
[4 2 2]
[5 2 1]
1400
[4 3 1]
[2 2 0]
1750
[3 3 2]
[3 2 1]
[4 2 0]
2100
YIG
YIG
YIG
YIG
YIG
YIG
1050
700
350
0
20
40
2-Theta Scale
Fig.2
60
80
(a)
(b)
Fig.3
(a)
(b)
Fig.4
(b)
(a)
Fig.5
(a)
(b)
Fig.6
(a)
(b)
Fig.7
(a)
(b)
Fig.8
70
PVDF
YIG at 1150°C by MCMO method
YIG at 950°C by self combustion method
YIG at 950°C by sol gel method
YIG at 1350°C by MCMO method
YIG at 1150°C by self combustion method
YIG at 1150°C by sol gel method
65
60
55
Initial permeability
50
45
40
35
30
25
20
15
10
5
0
0.0
7
2.0x10
7
4.0x10
7
6.0x10
Frequency(Hz)
(a)
7
8.0x10
8
1.0x10
8
1.2x10
60
50
Q-factor
40
PVDF
o
YIG by MCMO at 950 C
o
YIG by self combustion method at 950 C
o
YIG by sol gel method at 950 C
o
YIG by MCMO method at 1150 C
o
YIG by self combustion method at 1150 C
o
YIG by sol gel method at 1150 C
30
20
10
0
6
7
10
8
10
10
log f (Hz)
(b)
0.010
PVDF
o
YIG by self combustion method at 1150 C
o
YIG by sol gel method at 1150 C
o
YIG by sol gel method at 950 C
o
YIG by MCMO method at 1150 C
o
YIG by MCMO method at 1350 C
o
YIG by self combustion method at 1150 C
0.009
0.008
Relative loss factor
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
6
5.0x10
7
1.0x10
7
1.5x10
7
2.0x10
Frequency (Hz)
(c)
7
2.5x10
7
3.0x10
7
3.5x10
7
4.0x10
log scale
Relative loss factor
0.01
1E-3
1E-4
log F (Hz)
(d)
Fig. 9
1.0
YIG by sol gel at 950 °C
YIG by self combustion at 1150 °C
YIG by MCMO at 1350 °C
YIG by MCMO at 1150 °C
Magnetization (emu/g)
0.5
YIG by self combustion at 950 °C
YIG by sol gel at 1150 °C
0.0
-0.5
-1.0
-15000
-10000
-5000
0
5000
Applied field (Oe)
Fig 10
10000
15000
(a)
(b)
Fig 11