Advances in Nanoparticles, 2013, 2, 378-383
Published Online November 2013 (http://www.scirp.org/journal/anp)
http://dx.doi.org/10.4236/anp.2013.24052
Open Access ANP
Synthesis and Characterization of Ni-Zn Ferrite
Nanoparticles (Ni0.25Zn0.75Fe2O4) by Thermal
Treatment Method
Poh Lin Leng1, Mahmoud Goodarz Naseri2*, Elias Saion1, Abdul Halim Shaari1,
Mazaliana Ahmad Kamaruddin1
1Department of Physics, Faculty of Science, Universiti Putra Malaysia, Serdang, Malaysia
2Department of Physics, Faculty of Science, Malayer University, Malayer, Iran
Received August 14, 2013; revised October 2, 2013; accepted October 16, 2013
Copyright © 2013 Poh Lin Leng et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Cubic structured nickel-zinc ferrite nanoparticles (Ni0.25Zn0.75Fe2O4) have been synthesized by thermal treatment
method. In this procedure, an aqueous solution containing metal nitrates as precursors, polyvinyl pyrrolidone as a cap-
ping agent, and deionized water as a solvent were thoroughly stirred, dried at 353 K for 24 h, and crushed into powder
before calcination to remove organic matters and crystallize the particles. The structure and particle size were charac-
terized by X-ray powder diffraction and transmission electron microscopy. The average particle size increased from 7 to
25 nm with increase of calcination temperature from 723 to 873 K respectively. The magnetic properties were deter-
mined by vibrating sample magnetometer and electron paramagnetic resonance electron paramagnetic resonance at
room temperature. By increasing the calcinations temperatures from 723 to 873 K it showed an increase of the mag-
netization saturation from 11 to 26 emu/g and the g-factor from 2.0670 to 2.1220. The Fourier transform infrared spec-
troscopy was used to confirm the presence of metal oxide bands at all temperatures and the removal of organic matters
at 873 K.
Keywords: Thermal Treatment; Nickel Zinc Ferrite; Nanoparticles; Magnetic Property
1. Introduction
The last two decades have seen a remarkable progress in
the synthesis of spinel ferrites nanocrystals, aiming at a
better material with excellent chemical stability, low
magnetic coercivity, moderate saturation magnetization,
high permeability, high electrical resistivity and low
eddy current. In particular, the nickel-zinc (Ni-Zn) ferrite
nanocrystals have been extensively studied for their su-
per-paramagnetic properties, which are suitable for high-
frequency applications such as rod antennas and cores of
inductors and transformers [1,2]. The magnetic proper-
ties of ferrites of spinel structural formula AB2O4 are
mainly controlled by the divalent cations, which occupy
the tetrahedral A sites and the trivalent cation, which has
high degree affinity for octahedral B sites [3,4]. Zn fer-
rite bulk material has a normal spinel structure, where all
divalent cations are located on the tetrahedral sites and
trivalent cations all located on the octahedral sites. Ni
ferrites bulk materials on the other hand have an inverse
spinel structure, where half of trivalent cations occupy
the tetrahedral sites while the other half remain on octa-
hedral, while divalent cations all migrate to octahedral
positions. It has been shown that for the Ni-Zn ferrite
nanoparticles, octahedral sites prefer for Ni and tetrahe-
dral prefers for Zn [5]. Substituting Zn for Ni cations
leads to the formula (2
x
Zn

3
1x
Fe 
) (1x
N
i
3
1x
Fe 
)O4 (0 ≤ x
≤ 1), in which the first and second brackets indicate oc-
cupancy of the A and B sub-lattices respectively. Beside
the distribution of divalent and trivalent cations in the
spinel structure, the properties of Ni-Zn ferrite nanopar-
ticles are highly sensitive to the quantum confinement
effect of particle size, which in turn depends on the
method of preparation of the nanoparticles [6].
A variety of methods have been proposed for the syn-
thesis of Ni-Zn ferrite nanoparticles with controllable size,
shape, and chemical stability such as sol-gel methods [7],
*Corresponding author.

P. L. LENG ET AL. 379
thermal combustion method [8], citrate precursor route
[9], co-precipitation method [6,10], thermal plasma syn-
thesis [11], reverse micelle [12,13], hydrothermal [14],
micro-emulsion [15] and sonochemical reaction [16].
Some disadvantages of these methods include compli-
cated procedure, high reaction temperature, long reaction
time, and use of reduction agents, which are potential
upsetting the environment. In the present study, Ni-Zn
ferrite nanoparticles (Ni0.25Zn0.75Fe2O4) were synthesized
from an aqueous solution containing only metal nitrates
as precursors, polyvinyl pyrrolidone (PVP) as a capping
agent and deionized water as solvent by a simple thermal
treatment at moderate calcinations temperatures. No
other chemicals were added, thus this method offers the
advantages of simplicity, low reaction temperatures, a
low cost, and an environmentally friendly operation since
it produces no by-product effluents [17-20].
2. Experimental Procedure
2.1. Preparation
Iron (III) nitrate, Fe(NO3)3·9H2O, nickel(II) nitrate,
Ni(NO3)2·6H2O, and zinc nitrate, Zn(NO3)2·6H2O were
purchased from Acros Organics and PVP (MW = 10,000)
was supplied by Sigma Aldrich. All the chemical re-
agents were of research grade and used without further
purification. 3 g of PVP was dissolved in 100 ml of de-
ionized water at 343 K before mixing 0.2 mmol of iron
(III) nitrate, 0.025 mmol of nickel nitrate and 0.075
mmol zinc nitrate and the solution stirred for 2 hours. No
precipitation occurred in the solution. The brown solu-
tion was poured into a glass Petri dish and heated at 353
K in an oven for 24 hours to release most of the water.
The brown solid material was crushed into powder and
the samples were heated for 3 hours in alumina boat at
different calcination temperatures of 723, 773, 823 and
873 K to decompose the organic matters and crystallize
the nanoparticles.
2.2. Characterization
The textural and morphological characteristics of the pre-
pared Ni0.25Zn0.75Fe2O4 nanoparticles were studied with
several techniques to verify the particle size, shape and
size distribution as well as to explore the parameters of
interest. The structure was characterized by the XRD
technique using a Shimadzu diffract meter model XRD
6000 employing Cu Kα (0.1542 nm) radiation to generate
diffraction patterns from powder crystalline samples at
room temperature in 2θ range of 10˚ - 70˚. The infrared
spectra in the range 280 - 4000 cm−1 were recorded using
FTIR spectrometer (Perkin Elmer model 1650). The
FTIR spectra are used to confirm the presence of metal
oxide bands and the removal of organic matters at 873 K.
The structural and particle size of the calcined Ni0.25
Zn0.75Fe2O4 nanoparticles were determined at room tem-
perature by using transmission electron micrograph
(TEM) (JEOL 2010 UHR version microscopy) at an ac-
celerating electron voltage of 200 kV. The magnetization
was measured using a vibration sample magnetometer
(VSM) (Lake Shore 4700) at room temperature with a
maximum magnetic field of 15 kOe. The electron para-
magnetic resonance (EPR) spectra were recorded on a
JEOL JES-FA200 EPR spectrometer (JEOL, Tokyo, Ja-
pan) at room temperature.
3. Results and Discussion
3.1. Structural Studies
The FTIR spectra recorded for Ni0.25Zn0.75Fe2O4 nanopar-
ticles in the range between 280 cm−1 and 4000 cm−1 are
shown in Figure 1. The spectra give information about
the chemical and molecular structure changes in the syn-
thesized ferrites after calcination treatments. For all cal-
cined samples at calcination temperatures from 673 to
873 K, shown in Figures 1(a)-(d), two assigned absorp-
tion bands appear at 528 cm−1, which is attributed to
stretching vibration of octahedral group Fe-O stretching
band and that at 351 cm−1 are attributed to the tetrahedral
group Zn-O and Ni-O stretching bands. All absorption
peaks above 1000 cm−1 were attributed to covalent bonds
of PVP. The bending mode around 1602 - 1637 and
33,274 - 3390 cm−1 were associated with C = O stretch-
ing and O-H stretching vibration respectively. The ab-
sence of these peaks at 873 K confirmed the organic
sources were removed from the calcined samples and
pure Ni0.25Zn0.75Fe2O4 nanoparticles were obtained.
Figure 2 shows EDX pattern of the sample calcined at
873 K, which confirms the Ni, Zn, Fe and O peaks ap-
pearing along with the C substrate peak. No contaminat-
05001000 1500 2000 2500 3000 3500 4000 4500
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
Transmittance
wave number (cm-1)
(a)
(b)
(c)
(d)
351 528 1635 3274
351 528 1637 3390
351 5281602 3300
351 528
Figure 1. FTIR spectra of Ni0.25Zn0.75Fe2O4 nanoparticles
calcined at (a) 723, (b) 773, (c) 823 and (d) 873 K.
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P. L. LENG ET AL.
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0 1 2 3 4 5 6 7 8 9 10 11 12 13
Spectrum 3
O
Fe
Zn
N
i
Full Scale 785 cts Cursor: 13.525 (0 cts)keV
Fe Fe
N
i Zn
Figure 2. The EDX spectra of Ni0.25Zn0.75Fe2O4 nanoparticles grown on carbon at calcination temperature of 873 K.
ing elements from organic reagents, such as hydrogen or
nitrogen were detected.
Figure 3 shows the XRD diffraction patterns of the
Ni0.25Zn0.75Fe2O4 nanoparticles at 353 K and at calcina-
tion temperatures from 723 to 873 K. The diffraction
peaks show the reflection planes (111), (220), (311),
(400), (422), (333) and (440) which are consistent with
the standard powder diffraction reported from XRD li-
brary code (00-052-0279) and no other metal oxides
could be identified. The diffraction peaks become shar-
per when the calcinations temperature increased. It can
be said that all samples formed the spinal phase with a
face centered cubic structure (f.c.c). The particle size of
the ferrite nanoparticles has been estimated from the
XRD plane (311) by the Scherrer’s formula: d = 0.9 λ/β
cosθ, where d is the average particle size in nm, β is the
FWHM of the intensity measured in radians, λ is the
X-ray wavelength and θ is the Bragg angle. The average
particle size increased from 9 nm to 23 nm at calcination
10 20 30 40 50 60 70
0
2000
4000
6000
8000
10000
(e)
(d)
(c)
(b)
(a)
(440)
(333)
(422)
(400)
(311)
(220)
(111)
Intensity
2 Theta (degree)
Figure 3. XRD pattern of Ni0.25Zn0.75Fe2O4 nanoparticles at
(a) 353 K, and calcined at (b) 723, (c) 773, (d) 823 and (e)
tempera
873 K.
ture from 723 K to 873 K, as listed in Table 1.
d
si
3.2. Magnetic Studies
s of magnetization measured at
The TEM images in Figure 4 show the size, shape an
ze distribution of the Ni0.25Zn0.75Fe2O4 nanoparticles at
different calcination temperatures. The particle size in-
creased from 7 nm at 723 K to 25 nm at 873 K (Table 1).
The reason for the increase in the particle size is that the
surface of the nanoparticles melted and fused with the
neighboring particles at higher calcination temperatures
[17-20]. Thus it is possible to control particle size by the
calcination temperature. Smaller particle size has been
reported for Ni0.25Zn0.75Fe2O4 nanoparticles prepared by
wet co-precipitation routes with the average particle size
of about 4 nm [21] and 7 nm for Ni0.3Zn0.7Fe2O4 prepared
by co-precipitating aqueous solutions in alkaline medium
[6]. By ball-milling on Ni0.2Zn0.8Fe2O4 nanoparticles fab-
ricated by mechanochemical method, particle size of
about 11 nm was obtained but following annealing at 773
K the particle size increased to about 26 nm [22].
Figure 5 shows the curve
room temperature. Table 1 depicts the values of satura-
tion magnetization (Ms) and coercivity (Hc) of different
samples. Increasing the calcination temperatures from
723 K to 873 K, the Ms value increased from 11 emu/g to
26 emu/g and the coercivity value also increased from 7
to 29 G, when the particle size increased from 7 to 25 nm,
as listed in Table 1. The magnetization curves demon-
strate a typical superparamagnetic behavior. The Hc is in
direct proportional to the volume of single domain grains.
Therefore, Hc increased when the particles size increased.
Higher Ms values of about 30 emu/g have been achieved
for 15 nm Ni0.25Zn0.75Fe2O4 nanoparticles prepared by co-
precipitation [21], 22 emu/g for 6 - 7 nm Ni0.2Zn0.8Fe2O4
synthesized by forced hydrolysis in diethylenglycol [23]
and 28 emu/g for 6 - 8 nm Ni0.35Zn0.65Fe2O4 obtained by
thermal decomposition [6].

P. L. LENG ET AL. 381
(a)
(b)
(c)
(d)
Figure 4. TEM images of Zn0.75Fe2O4 nanoparticles
calcined at (a)723, (b) 773, (c) 823 and (d) 873 K.
ed a thermal treatment method for the
Ni0.25
Figure 6 shows the EPR spectra of the samples cal-
cined at (a) 723, (b) 773, (c) 823 and (d) 873 K. Peak-to-
peak line width (ΔHpp), resonant magnetic field(H),and
g-factor are three parameters that characterize the mag-
netic properties. The g-factor can be calculated according
to the equation: g = hν/βH where h is Planck’s constant, ν
is the microwave frequency, β is the Bohr magneton
(9.274 × 10−21 erg·G−1), and H is resonant magnetic field.
The values of g-factor increased from 2.0670 to 2.1220
correspond to the decrease of the resonance magnetic
field from 3170 to 3090 G with the increase of calcina-
tion temperature from 723 K to 873 K.
4. Conclusion
This paper present
30
-10000 -50000500010000
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
M (emu/g)
H (G)
(a)
(b)
(c)
(d)
Figure 5. VSM curves of Ni0.25Zn0.75Fe2O4 nanoparticles ca
cined at (a)723, (b) 773, (c) 823 and (d) 873 K. l-
-2000-100001000 2000 3000 40005000 6000 7000 800
0
-2000
-1500
-1000
-500
0
500
1000
1500
2400 2700 3000
1000
1200
1400
B
A
(a)
(b)
(d)(c)
intensity
M agnetic field (G)
Figure 6. EPR spectra of Ni0.25Zn0.75Fe2O4 nanoparticl
calcined at (a) 723, (b) 773, (c) 823 and (d) 873 K. es
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P. L. LENG ET AL.
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382
na magnetic
Ni0.25Zn0.75Fe2O4 Calcinations Average particle Average particle Saturation magnetization,Coercivity Peak to peak line factorResonance
Table 1. The average particle sizes (nm) of Ni0.25Zn0.75Fe2O4oparticles determined from XRD and TEM andn
properties observed from VSM and EPR at room temperature.
nanoparticles temperature (K) size XRD (nm) size TEM (nm)Ms (emu/g) field Hc (G)width ΔHpp (G) g- field, Hr (G)
Ni-2.0670Zn ferrite 1 723 9 7 11.414 7 758 3170
Ni-Zn ferrite 2 773 11 9 15.785 10 755 2.08853140
Ni-Zn ferrite 3 823 14 13 20.320 26 753 2.10503118
Ni-Zn ferrite 4 873 23 20 26.447 29 750 2.12203090
nthesis of Ni0.25Zn0.75Fe2O4 nanocrystals with grain
by the Ministry of Higher
[1] A. Goldman, “logy,” 2nd Edition,
6/j.jmmm.2006.02.031
sy
size ranging from 7 to 25 nm at the calcination tempera-
tures from 723 to 873 K as measured by XRD and TEM.
The PVP stabilized the particles and prevented them
from agglomerating. The FTIR measurement confirmed
the removal of all organic matters and leaving pure metal
oxides at 873 K. The VSM results showed that the satu-
ration magnetization increased from 11 emu/g to 26 emu/
g and the coercivity value increased from 7 to 29 G at
calcination temperatures from 723 K to 873 K due to the
increasing of the volume of single domain grains. The
values of g-factor increases with increase of calcination
temperature and particle size were increased. This simple
method, which is cost-effective and environmentally
friendly, produces no toxic byproduct effluents and can
be used to fabricate pure, crystalline spinel ferrite nano-
crystals.
5. Acknowledgements
This work was supported
Education of Malaysia under the FRGS grant. The au-
thors would also like to thank staff of the Faculty of Sci-
ence and the Bioscience Institute of University Putra
Malaysia, who had contributed to this work.
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