Journal of Alloys and Compounds 502 (2010) 279–282
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Rietveld analysis and Mössbauer spectroscopy studies of nanocrystalline
hematite -Fe
2
O
3
O.M. Lemine
a,∗
, M. Sajieddine
b
, M. Bououdina
c
, R. Msalam
d
, S. Mufti
d
, A. Alyamani
e
a
Department of Physics, College of Sciences, Imam University, Riyadh, Saudi Arabia
b
Laboratoire de Physique et Mécanique des Matériaux, Sultan Moulay Slimane University, Béni-Mellal, Morocco
c
Department of Physics, College of Science, University of Bahrain, Bahrain
d
Radiation Technology Center, KACST, Riyadh, Saudi Arabia
e
National Nanotechnology Research Centre, KACST, Riyadh, Saudi Arabia
article info
Article history:
Received 9 March 2010
Received in revised form 9 April 2010
Accepted 24 April 2010
Available online 5 May 2010
Keywords:
Nanoparticles
Hematite
Ball milling
Mössbauer
X-ray diffraction
Rietveld
abstract
The effect of high energy ball milling on the hematite for milling periods of times ranging from 1 to 48 h
was investigated by Rietveld analysis based on XRD patterns and Mössbauer spectroscopy. An expansion
of the unit cell parameters was observed. Both Scherrer method and Rietveld analysis show an evident
decrease of the grain size with the increase of the milling time. Moreover, some dependence of the lattice
parameters on the grain size was observed. Mössbauer spectroscopy measurements reveal that there
are two kinds of particles which co-exist in the sample: nanostructured and micrometric hematite. The
magnetic hyperfine field is affected by the grain size.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
In recent years, nanoparticle systems have attracted increasing
attention due to their immense technological applications [1,2].
Many nanoparticle systems have been investigated particularly
the magnetic nanoparticles in the field of nanoscience and nan-
otechnology, because of the unique and novel physico-chemical
properties that can be attained according to their size, morphol-
ogy and engineering form [3–5]. Hematite nanoparticles (-Fe
2
O
3
)
have potential applications into many areas such as magnetism,
catalysis, electrochemistry, and biotechnology. Several groups have
been interested by the mechanical alloying of hematite [6–9]. Zduji
et al. [16] studied the mechanochemical treatment of -Fe
2
O
3
pow-
der in air and oxygen atmospheres using a conventional planetary
ball mill. They observed that -Fe
2
O
3
completely transforms to
Fe
3
O
4
, and for prolonged milling to the Fe
1-x
O phase, either in air
or oxygen atmosphere. The transformation of -Fe
2
O
3
to Fe
3
O
4
on wet-milling -Fe
2
O
3
under low milling energy conditions in
vacuum was investigated by Campbell et al. [15]. Randrianantoan-
dro et al. [6] studied the phase transformation from hematite to
maghemite during high energy ball milling in ethanol. They show
∗
Corresponding author.
E-mail address: leminej@yahoo.com (O.M. Lemine).
that maghemite (-Fe
2
O
3
) can be directly produced from hematite
(-Fe
2
O
3
) after 48 h milling time. Recently, we studied the syn-
thesis and structural characterization of hematite nanoparticles
produced by dry mechanical alloying [11,17].
In this report, the effect of ball milling time on the hematite
was investigated. Structure (phase formation) and microstructural
parameters (crystallite size) evolution were analysed by means of
Rietveld analysis. Magnetic properties were measured and anal-
ysed by means of Mössbauer spectroscopy measurements.
2. Experimental
Commercial -Fe2O3 powder was used as the starting material. The mechanical
milling was carried out in a planetary ball mill Fritsch Pulverisette 6. The powder
was ground in vial with 200 g of mixture 1:1 in weight of stainless steel balls (10 and
15 mm in diameter). Different milling times were used (1, 6, 12, 24 and 48 h) and the
sample to balls weight ratio was fixed to 1:10 and the milling intensity was fixed
to 250 rpm. X-ray diffraction (XRD) measurements were performed using Shimadzu
diffractometer (–2) by using Cu-K radiation ( = 1.5418 Å). Qualitative and quan-
titative analyses were carried by the Rietveld method using Rietan’s programme
[12]. Both refined lattice parameters and the crystallite size were reported.
The crystalline size was also calculated using Schererrer formula:
D =
K
B cos
(1)
In this case, the peak width B (in rad) was determined as full width at half-
maximum (FWHM) by a Gaussian fitting.
57
Fe Mössbauer spectroscopy provided relevant information concerning the
valence state of iron atoms and magnetic hyperfine characteristic of iron oxide
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.04.175