ISSN 10876596, Glass Physics and Chemistry, 2012, Vol. 38, No. 4, pp. 357–360. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.A. Osipov, G.G. Korinevskaya, L.M. Osipova, V.A. Muftakhov, 2012, published in Fizika i Khimiya Stekla.
357
INTRODUCTION
Titanium oxide is an important component of a large
amount of glasses and enamels and significantly affects
their properties. Numerous studies of Ticontaining
glasses have shown that the influence of TiO
2
on the
properties of these glasses depends on the structural
position of Ti atoms in the random glass network.
Depending on the composition of the compound, the
coordination number of Ti atoms may be 4, 5, or 6. In
the TiO
4
group, titanium is located inside the tetrahe
dron with oxygen atoms in the heads. In natural com
pounds, tetrahedral coordination of Ti atoms is unlikely
and occurs mainly when Ti is a trace atom in the struc
ture of formally Tifree mineral. To a greater extent,
such coordination is peculiar to Ti atoms in the struc
tures of TiO
2
–SiO
2
glasses of various compositions [1–
4]. At a coordination number of 5 (TiO
5
group), Ti may
occur inside a tetragonal prism or trigonal bipyramid.
Frensoite (Ba
2
TiSi
2
O
8
), Na
2
TiSiO
5
, and K
2
Ti
2
O
5
are
examples of such compounds [3, 5]. In all three TiO
2
polymorphic modifications—rutile, anatase, and broo
kite—Ti occurs in sixfold coordination by oxygen,
which corresponds to an octahedron (Poling’s polyhe
dron). Simultaneous coexistence of two types of struc
tural positions of Ti atoms variously manifested in the
glass properties is often observed in Ticontaining
glasses [5–8], so the question of Ti coordination in
glasses is important and still open.
This work presents Raman spectroscopic studies of
the structure of TiO
2
–Na
2
O–SiO
2
glasses in the sec
tion with a constant SiO
2
/Na
2
O ratio of 1.5 and vari
able concentration of TiO
2
.
EXPERIMENTAL TECHNIQUE
The compositions of the studied glasses are shown
in Table 1. The glasses were synthesized from high
purity SiO
2
, TiO
2
, and Na
2
CO
3
. The initial reagents
were previously dried at 110°C for 2 h, and, later, the
required samples were thoroughly mixed in a mortar
with alcohol and dried again at the same temperature.
The obtained batch (15 g) was placed into a platinum
crucible and melted in an electric oven at 1200°C up to
complete melt homogenization. Then, the melt was
poured in air into a small platinum crucible and cooled
to room temperature. Later, the sample in the crucible
was used for the recording of Raman spectra.
The Raman spectra were recorded on an experi
mental device based on the double DFS24 mono
chromator specially created for measurement in a
Titanium Coordination in TiO
2
–Na
2
O–SiO
2
Glasses
of xTiO
2
· (100 – x) [2Na
2
O · 3SiO
2
] (0 ≤ x ≤ 30) Composition
Based on Raman Spectroscopy
A. A. Osipov, G. G. Korinevskaya, L. M. Osipova, and V. A. Muftakhov
Institute of Mineralogy, Ural Branch, Russian Academy of Sciences, Miass, Chelyabinsk oblast, 456317 Russia
email: 100123@mineralogy.ru
Received May 12, 2011
Abstract—The structural position of Ti
4+
ions in TiO
2
–Na
2
O–SiO
2
glasses of xTiO
2
· (100 – x) [2Na
2
O · 3SiO
2
]
(0 ≤ x ≤ 30) composition has been studied with Raman spectroscopy. The analysis of spectra recorded has
demonstrated that Ti
4+
ions in the studied glasses can be in two structural groups—TiO
5
and TiO
6
. Titanium
ions with a coordination number of 5 are present in the structure of all Ticontaining glasses, whereas the
highly coordinated state exists at x > 10 mol % TiO
2
.
Keywords: spectroscopy, TiO
2
–SiO
2
glasses, structure
DOI: 10.1134/S1087659612040098
Glass compositions (mol %) and their designations
Glass
designation
Composition
0TNS 40Na
2
O · 60SiO
2
1TNS 1TiO
2
· 99(40Na
2
O · 60SiO
2
)
5TNS 5TiO
2
· 95(40Na
2
O · 60SiO
2
)
10TNS 10TiO
2
· 90(40Na
2
O · 60SiO
2
)
15TNS 15TiO
2
· 85(40Na
2
O · 60SiO
2
)
20TNS 20TiO
2
· 80(40Na
2
O · 60SiO
2
)
25TNS 25TiO
2
· 75(40Na
2
O · 60SiO
2
)
30TNS 30TiO
2
· 70(40Na
2
O · 60SiO
2
)