ISSN 0020-1685, Inorganic Materials, 2007, Vol. 43, No. 6, pp. 675–681. © Pleiades Publishing, Inc., 2007.
Original Russian Text © A.N. Moiseev, V.V. Dorofeev, A.V. Chilyasov, A.M. Kut’in, V.G. Pimenov, V.G. Plotnichenko, V.V. Koltashev, 2007, published in Neorganicheskie Materi-
aly, 2007, Vol. 43, No. 6, pp. 762–768.
Preparation of High-Purity TeO2–ZnO Glass Batches
a
a
a
a
a
A. N. Moiseev , V. V. Dorofeev , A. V. Chilyasov , A. M. Kut’in , V. G. Pimenov ,
b
b
V. G. Plotnichenko , and V. V. Koltashev
a Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences,
ul. Tropinina 49, Nizhni Novgorod, 603950 Russia
b Fiber Optics Research Center, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119333 Russia
e-mail: moiseev@ihps.nnov.ru
Received January 9, 2007
Abstract—Tellurium oxide–zinc oxide glass batches have been prepared through chemical vapor deposition
from tellurium and zinc alkyl compounds in an oxyhydrogen flame onto the lateral surface of rotating cylindri-
cal substrates. The composition of the deposits has been shown to be determined by the relative amounts of the
metalorganic precursors in the gas phase. Varying the deposition conditions, we obtained both amorphous and
crystalline deposits, with concentrations of metallic impurities below 1 ppmw. Melting the deposits, we pre-
pared high-purity (TeO2)1 – x(ZnO)x (0.15 ≤ x ≤ 0.35) glasses.
DOI: 10.1134/S0020168507060210
INTRODUCTION
precursors in the oxidation process enables the prepara-
tion of purer materials, as was illustrated by the exam-
ple of zinc [4].
Tellurite glasses possess a broad transmission win-
dow (0.4–6 µm) and highly nonlinear optical proper-
ties, are chemically stable, and dissolve high levels of
rare-earth elements. These advantages make them
potentially attractive materials for active components
of optical fiber communication systems [1, 2].
A standard approach to the preparation of tellurite
glasses is to melt an oxide batch in a platinum or gold
crucible and, after homogenization, to cool the melt [2].
The purity of the resulting glass depends on the impu-
rity concentrations in the batch components and in the
gaseous environment of the melting process. The purity
of commercially available oxides is, however, below
the level required for advanced optical fiber applica-
tions.
The purest quartz glass for the fabrication of optical
fibers is commonly prepared by chemical vapor deposi-
tion (CVD) [3]. The key step of this process is the gas-
phase oxidation of silicon tetrachloride and germa-
nium, phosphorus, and boron halides, which are added
to the reaction mixture in order to control the refractive
index profile in the fibers. Oxide powders can be depos-
ited using an oxyhydrogen flame. This method has
important advantages which offer the possibility of pre-
paring high-purity quartz glass and to maintain its
purity during subsequent fabrication of optical fibers.
In view of this, it is reasonable to apply a similar pro-
cess in the preparation of high-purity tellurite glasses.
The objective of this work was to develop a process
for the preparation of high-purity íÂé2–ZnO glass
batches via the oxidation of íÂ(CH3)2 and Zn(CH3)2 in
an oxyhydrogen flame and to determine the impurity
and phase compositions of the resultant batches.
THERMODYNAMIC ANALYSIS
As tellurium and zinc precursors, we considered
dimethyltellurium (DMT), Te(CH3)2; diethyltellurium,
Te(C2H5)2; dimethylzinc, Zn(CH3)2; and diethylzinc,
Zn(C2H5)2. These MOPs offer sufficiently high volatil-
ity (Table 1) and are highly reactive with oxygen and
water vapor, which are present in oxyhydrogen flames.
Based on preliminary results, preference was given to
the methyl compounds. Diethyltellurium and diethylz-
inc have lower vapor pressures (Table 1). With these
precursors, the deposition rate of mixed oxides was no
higher than 1–2 g/h.
Table 1. Properties of tellurium and zinc alkyl compounds
Com-
Boiling p, mm Hg Temperature-dependent
pound point, °C (t = 10°C)
vapor pressure
One attractive glass-forming system is íÂé2–ZnO,
which has a broad glass-forming region: 9–40 mol %
ZnO. For both tellurium and zinc, there are sufficiently
volatile metalorganic precursors (MOPs) available
commercially as high-purity reagents. The use of such
Te(CH3)2
Te(C2H5)2
Zn(CH3)2
Zn(C2H5)2
93
137
44
23.9
3.9
logp = –1865/T + 7.97
logp = –2093/T + 7.99
logp = –1560/T + 7.802
logp = –2109/T + 8.28
196
6.7
118
675