Journal of Alloys and Compounds 509 (2011) 7373–7380
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Review
Structural impact of tungsten ions on ZnO–Sb
2
O
3
–As
2
O
3
glass system
S. Bala Murali Krishna, D. Krishna Rao
∗
Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur 522 510, Andhra Pradesh, India
article info
Article history:
Received 14 March 2011
Received in revised form 18 April 2011
Accepted 19 April 2011
Available online 27 April 2011
Keywords:
Amorphous materials
Rapid-solidification
Quenching
Dielectric response
Optical properties
Electron paramagnetic resonance
X-ray diffraction
abstract
Five glasses in the quaternary system 5 ZnO–(50 - x) As
2
O
3
–45 Sb
2
O
3
: x WO
3
with the values of x ranging
from 0 to 20 mol% (in steps of 5 mol%) are prepared. The samples are characterized by X-ray diffraction,
scanning electron microscopy, energy dispersive spectroscopy (EDS) and differential thermal analysis
(DTA) techniques. The DTA studies have indicated that the glass forming ability decreases with the
increasing content of WO
3
. A number of studies, like, spectroscopic (optical absorption, IR, Raman, ESR
spectra) and dielectric studies (dielectric constant ε, loss tan ı, a.c. conductivity
a.c.
) over a wide range of
frequency and temperature and dielectric break down strength at room temperature, have been carried
out and are analysed in the light of different oxidation states and environment of tungsten ions in these
glasses. These glasses have potential photonic applications.
© 2011 Elsevier B.V. All rights reserved.
Contents
1. Introduction .......................................................................................................................................... 7373
2. Materials and methods ............................................................................................................................... 7374
3. Experimental ......................................................................................................................................... 7374
4. Results ................................................................................................................................................ 7374
5. Discussion ............................................................................................................................................ 7378
6. Conclusions .......................................................................................................................................... 7380
References ........................................................................................................................................... 7380
1. Introduction
Tungsten ions are expected to have profound influence on the
physical properties of antimony arsenate glasses, for the simple rea-
son that the tungsten ions exist in different valance states viz., W
6+
,
W
5+
and also in W
4+
state, regardless of the oxidation state of the
tungsten ion in the starting glass batch [1–4] as per the following
thermo reversible disproportionate reaction:
W
5+
+ W
5+
↔ W
4+
+ W
6+
Tungsten oxide participates in the glass network with differ-
ent structural units like WO
4
(Td) and WO
6
(Oh) of W
6+
ions
and W
5+
O
3
-
(Oh) of W
5+
ions [5]. The concentration of different
∗
Corresponding author. Tel.: +91 863 6458142 (R)/2346380 (O);
fax: +91 863 2293378.
E-mail addresses: krdhanekula@yahoo.co.in, sbmkkrishna@yahoo.co.in
(D. Krishna Rao).
structural groups of tungsten ions with different oxidation states
present in the glass matrix at a given temperature depends on the
quantitative properties of modifiers, glass formers, size of ions in
the glass structure, mobility of the modifier cation etc. W
5+
ions
are well known paramagnetic ions. The presence of tungsten in
antimony arsenate glasses, further, makes the glasses suitable for
optoelectronic devices since they exhibit photochromism and elec-
trochromism properties [6,7]. The structural groups of tungsten
oxide are expected to alternate with AsO
3
, AsO
4
and SbO
3
struc-
tural groups and are likely to influence the physical properties of
antimony arsenate glasses to a large extent (since some of the vibra-
tional modes of these groups lie in the region of SbO
3
and AsO
3
structural groups). The presence of metal oxide like ZnO, between
the long chain molecules in the vicinity of tungsten ions in the
antimony arsenate network, the symmetry and/or covalency of
the glass at the W
6+
ions will be varied. Additionally, the varia-
tions in the oxidation states of antimony ions are also expected
to modify the crystal field around tungsten ions in the host glass
network. As a result, the structural probing of tungsten ions on
0925-8388/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2011.04.100