Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 7, pp. 1226−1229.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
Ya.A. Kalymon, O.I. Bilan’, O.I. Kuntyi, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 7, pp. 1130−1133.
AND CORROSION PROTECTION OF METALS
Morphology of Tellurium Electrolytically Deposited
in a Pulsed Mode
Ya. A. Kalymon, O. I. Bilan’, and O. I. Kuntyi
Lvivska politekhnika National University, Lviv, Ukraine
Received October 21, 2008
Abstract—Morphology of tellurium deposits produced by pulsed electrolysis of 0.005–0.05 M TeCl
in dimethyl sulfoxide was studied. The effect of the TeCl
concentration and pulsed current parameters on the
structure of electrolytically deposited tellurium films was examined.
Pulsed electrolysis is one of the most efﬁ cient ways
to form the structure of metal and alloy deposits [1–4].
This is also a promising method for obtaining nanosize
dispersed materials [1, 5, 6]. Most of studies of the
pulsed deposition mode refer to aqueous solutions, and
only those carried out in the very recent years, to organic
[4, 7] or aqueous-organic solvents . Some of organic
solvents and, especially, aprotic solvents are distinguished
by high donor properties and electrochemical stability
, as well as by indifference toward numerous metals.
This enables deposition of metals at high potentials and
provides formation of a stable morphology of deposits,
without side cathodic reactions.
This study, devoted to deposition of tellurium by
electrolysis of TeCl
in an organic aprotic solvent dimethyl
sulfoxide (DMSO) with a pulsed current, proceeds with
systematic analyses of the electrochemistry of tellurium
 and other metals [6, 7] in a nonaqueous medium.
Tellurium was deposited in a 50-cm
three-electrode glass electrolyzer in a 0.005–0.05 M
solution of TeCl
in DMSO at temperatures of 20–60°C.
Tellurium tetrachloride was synthesized by a procedure
described in  and dissolved in DMSO of chemically
pure grade. The edge of a graphite rod 6 mm in diameter
served as the working electrode. Its nonworking surface
was insulated with a ﬂ uoroplastic tape. Prior to each
experiment, the working surface of the electrode was
trimmed with ﬁ ne emery paper, polished with a velvet
fabric, and washed with isopropanol. The role of the anode
was played by lump tellurium in a ﬂ uoroplastic basket
with a platinum current lead. The potentials are given
relative to a saturated silver chloride electrode placed in
a glass vessel with a saturated quinoline solution of KCl
and connected to the electrolyzer by a Luggin–Haber
capillary. An IPC-Pro potentiostat was used in electrolysis
in steady-state and pulsed modes. The potential pulses
used were of rectangular shape, the pulse and pause
, were 0.02–5.0 s. The deposits obtained
were washed, without being removed from the graphite
electrode, with DMSO and then with isopropanol, dried
in air at 60°C, and examined with REMMA-102-02 and
EVO 40XVP scanning electron microscopes.
It has been shown previously that a steady-state
electrolysis of TeCl
in dimethyl sulfoxide solutions
yields smooth and shining tellurium ﬁ lms . However,
dispersed tellurium starts to be formed in a 0.05 M solution
in DMSO at E
> |–1 V|. It was found that use
of a pulse mode makes it possible to obtain tellurium
ﬁ lms at more negative potentials (up to –2.0...2.5 V). At
the same time, the sizes of crystalline grains constituting
a ﬁ lm and their conﬁ gurations and packing modes are
strongly different. For example, the size of crystallites
formed in the dc mode is 0.7–1.1 μm (Fig. 1a), and that
for the pulsed mode, 0.2–0.4 μm (Fig. 1b). Possibly, this
is due to adsorption of electron-donor DMSO molecules