Raman spectroscopy study of products of reactions of zirconium and hafnium tetrachlorides with indium and thallium monochlorides

Article abstract of DOI:10.1134/S1070427213050133

Reactions of ZrCl₄ and HfCl₄ with InCl and TlCl accompanied by formation of several solid complex compounds were studied by the Raman spectroscopy method.

Full text of DOI:10.1134/S1070427213050133

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 5, pp. 687−690. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.B. Salyulev, E.G. Vovkotrub, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 5, pp. 740−743.
PHYSICOCHEMICAL STUDIES
OF TECHNOLOGIES
Raman Spectroscopy Study of Products of Reactions
of Zirconium and Hafnium Tetrachlorides with Indium
and Thallium Monochlorides
A. B. Salyulev and E. G. Vovkotrub
Institute of High-Temperature Electrochemistry, Ural Brach of Russian Academy of Sciences, Yekaterinburg, Russia
Received January 28, 2012
Abstract—Reactions of ZrCl4 and HfCl4 with InCl and TlCl accompanied by formation of several solid complex
compounds were studied by the Raman spectroscopy method.
DOI: 10.1134/S1070427213050133
Separation of zirconium and hafnium is among the
hardest problems of the nuclear power construction ma-
terials engineering. The both elements essentially differ
from each other in nuclear characteristics, whereas their
ionic and atomic radii are almost identical owing to the
lanthanide contraction, therefore chemical properties
and crystallochemical characteristics of zirconium and
hafnium compounds are very close to each other [1–3].
Refining of the physicochemical characteristics of com-
pounds of the elements-twins under consideration, espe-
cially detecting distinctions in their behavior in various
systems, can essentially facilitate the purposeful search-
ing for the methods of their separation and purification.
complex anionic groups MCl62– and M2Cl92– increases in
the series from Cs+ to Li+ [1–13]. In contrast to LiHf2Cl9,
the LiZr2Cl9 compound is not formed in the systems with
lithium chloride even at room temperature [10].
To solve the problem whether there are monochlorides
of other metals (except for LiCl), which differently react
with zirconium and hafnium tetrachlorides, we have
investigated material compositions of ZrCl4 and HfCl4
fusion cakes with InCl and TlCl, using the modern struc-
ture-sensitive Raman spectroscopy method. We failed to
find any information on the fusion diagrams of the cor-
responding binary systems, except for ZrCl4–TlCl [13].
Melts and fusion cakes of zirconium and hafnium
tetrachlorides with chlorides of monovalent metals are
formed in various stages of processing mineral raw ma-
terials by chlorine metallurgy methods [1, 2]. So far it
was found in [1–13], presumably by the methods of ther-
mal analysis, tensimetry, and Raman spectroscopy, that
stable congruently melting chloride complexes Me2MCl6
exist in all binary systems MCl4–MeCl (M = Zr, Hf;
Me = Cs–Li, Tl), and less stable MeM2Cl9 compounds
exist in almost all such systems (except for the systems
ZrCl4–LiCl and ZrCl4–TlCl). The thermal stability of the
mentioned chloride complexes (in relation to splitting
off ZrCl4 and HfCl4) is reduced as the counterpolarizing
action of a singly charged cation on chloride anions in
EXPERIMENTAL
High-purity chlorides were used in the work. Yellow
modification of InCl stable at room temperature was
synthesized by alloying InCl3 (obtained by chlorination
of the metal by dry chlorine) with a calculated amount
of IN-00-grade metal indium in evacuated and soldered
quartz ampoules [14]. TlCl was precipitated from aqueous
solutions of analytical-grade Tl2CO3 by chemically-pure
grade hydrochloric acid with following triple recrys-
tallization from solutions in distilled H2O [14]. Then
the salt was carefully dried at gradual heating (within
several hours) in vacuum up to 130°С. Raman spectra
of the synthesized samples of solid InCl and TlCl cor-
687

688
SALYULEV, VOVKOTRUB
Table 1. Experimental values of vibrational frequencies ν in
Raman spectra of ZrCl62– and HfCl62– groups in fusion cakes
of zirconium and hafnium tetrachlorides with indium and thal-
lium monochlorides
glass microcells were investigated under a Leica DMLM
microscope (objectives ×50 and ×100) of the same spec-
trometer. More detailed description of separate prepara-
tive techniques and of the procedure of recording spectra
are given in the papers [10, 11, 17].
ν1(A1g)
ν5(F2g)
The Raman spectroscopy study of salt fusion cakes
of various compositions fulfilled in this work points to
the fact that zirconium and hafnium tetrachlorides form
Me2MCl6 crystal compounds with indium and thallium
monochlorides [13], as well as with chlorides of all
alkali metals [1, 2]. We detected the presence of such
compounds in fusion cakes by ν1(А1g) and ν5(F2g) lines of
the octahedral groups ZrCl62– and HfCl62– (Figs. 1c and
2c; Table 1), which are present also in other zirconium
and hafnium complex compounds [5–12, 18, 19] with
close characteristic vibrational frequencies. The ν2(Eg)
bands of the both groups have a very low intensity and
practically are not exhibited in the spectra. In the fusion
cakes with a high ZrCl4 or HfCl4 concentration there
are also bands of individual solid tetrachlorides (the C2h
symmetry group with two metal atoms in a unit cell [1,
2, 7, 10]): Ag and Bg type vibrations: 412, 394, 310, 284,
221, 143, 134, and 102 cm–1 in case of ZrCl4 (Fig. 1a)
and 396, 371, 299, 289, 233, 147, 127, and 105 cm–1 in
case of HfCl4 (Fig. 2a).
Compound
cm–1
In2ZrCl6
Tl2ZrCl6
333
335
149
155
In2HfCl6
Tl2HfCl6
340
341
154
160
Table 2. Experimental values of vibrational frequencies ν in
Raman spectra of Hf2Cl9– groups in fusion cakes of hafnium
tetrachloride with indium and thallium monochlorides
Assignment of frequencies, cm–1
Compound
ν1(A1') ν2(A1') ν9(E') ν11(E') ν12(E') ν16(E'')
InHf2Cl9
TlHf2Cl9
370
371
309
309
256
257
153
154
125
126
110
111
responded to the published data [15, 16]. To synthesize
ZrCl4 and HfCl4, were synthesized by the action of dry
hydrogen chloride on the high-purity metals obtained by
the iodide procedure and distilled in a flow of the same
gas into quartz ampoules. Then specified amounts of InCl
or TlCl powders were loaded in these ampoules (in a dry
box with P2O5 in nitrogen atmosphere), and after that the
ampoules were evacuated and soldered. The reagents
(salts) distributed in the form of a thin layer along sides
of the quartz ampoules (about 5 mm in diameter and 100
mm in length) in a horizontal position were first fused in
a blowpipe flame and rapidly cooled. Then the ampoules
were repeatedly heated up within 7–10 h at 230–350°С in
an electric furnace with a metal block (step-by-step tem-
perature increase, exposure within 4–5 h at 330–350°С),
then slowly cooled up to room temperature within 4–5 h.
Results of the spectroscopic investigations of samples
taken from both surface and deep-seated sections of salt
fusion cakes and placed in soldered ampoules or glass
microcells, testify also that after alloying components in
binary systems ZrCl4–InCl and ZrCl4–TlCl under various
conditions other complex compounds are not formed, as
in the Raman spectra of the fusion cakes containing more
than 33 mol % of the tetrachloride at its various concen-
trations (38, 44, 56, 67, and 73 mol % of ZrCl4) only
a superposition of bands of the crystalline compounds
ZrCl4 + In2ZrCl6 and ZrCl4 + Tl2ZrCl6 were observed.
As an example one of such spectra is shown in Fig. 1b.
On the contrary, in the Raman spectra of fusion
cakes of hafnium tetrachloride with indium and thal-
lium monochlorides we have revealed additional groups
of bands with a specific frequency set (Table 2; Fig. 2b)
To eliminate undesirable side action of air moisture,
selected sections of samples under analysis (fusion cakes)
were investigated directly through sides of the reaction
soldered ampoules under a microscope of a Renishaw
U1000 spectrometer (Great Britain production,Ar+ laser,
power up to 25 mW, objectives ×20 and ×50). In addi-
tion separate particles taken from various sections of
fusion cakes and transposed in a dry box into hermetic
–
corresponding to the vibrations of the anionic Hf2Cl9
group of the D3h symmetry in the composition of solid
MeHf2Cl9 complex compounds analogous to MeZr2Cl9
[7–12]. Pressures of ZrCl4 and HfCl4 in saturated vapors
above these complex compounds are lower than above
the pure solid tetrachlorides [4, 8–10]. Obviously, the fu-
sion cakes of HfCl4 with InCl and TlCl contain chloride
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RAMAN SPECTROSCOPY STUDY OF PRODUCTS OF REACTIONS
689
a
a
b
b
c
c
Fig. 1. Raman spectra of compounds (a) ZrCl4, (b)
ZrCl4 + In2ZrCl6 (a fusion cake with ZrCl4 concentration
of 67 mol %), and (c) In2ZrCl6 in ZrCl4–InCl fusion cakes.
(I) Intensity (relative units), (ν) wave number (cm–1); the
same for Fig. 2.
Fig. 2. Raman spectra of compounds (a) HfCl4, (b)
InHf2Cl9, and (c) In2HfCl6 in HfCl4–InCl fusion cakes.
Thus, the formation of MeHf2Cl9 complex compounds
in fusion cakes of zirconium and hafnium tetrachlorides
with indium and thallium monochlorides (as well as with
lithium monochloride [10]) was revealed by means of Ra-
man spectroscopy, whereas MeZr2Cl9 compounds were
not detected. These experimental data agree with a trend
of formation relatively stronger chloride complexes of
hafnium tetrachloride in anhydrous systems, as compared
with ZrCl4 [1–3, 21]. The factor of presence or absence
of complex compounds can be used in the technology of
hafnium and zirconium separation.
complexes of the same stoichiometric composition as in
the fusion cakes with CsCl, RbCl, KCl, NaCl, and LiCl.
In contrast to the fusion cakes with ZrCl4 (Fig. 1), bands
of individual Me2MCl6,MeM2Cl9, and MCl4 compounds
with Me = In, Tl (Fig. 2, Tables 1 and 2) or superpositions
of bands of MCl4 + MeM2Cl9 and MeM2Cl9 + Me2MCl6
(in fusion cakes with concentrations 73 or 56, 44, and
38 mol % of HfCl4, respectively) were detected in Ra-
man spectra of InCl and TlCl fusion cakes with HfCl4
in high concentrations (33, 44, 56, 67, 72, and 100 mol
%). Raman spectra of individual and complex Zr(IV)
and Hf(IV) chlorides are highly specific [7–12, 18–20],
which makes easier their identification: Raman spectra
of the compounds containing various chloride groups of
tetravalent metals differ essentially (as, for example, is
seen in Fig. 1 or Fig. 2). At the same time Raman spectra
of similar (related) compounds, in particular InHf2Cl9 and
TlHf2Cl9 (Table 2), MeHf2Cl9 (Me = Cs–Li) and MeZ-
r2Cl9 (Me = Cs–Na) [4, 7–12, 20] are similar and close in
the numbers of bands, vibrational frequencies, and band
intensity ratios. Octahedral coordination groups MCl6
The systematic study of vibrational spectra of ZrCl4
and HfCl4 complex compounds with chlorides of mono-
and divalent metals have shown that the frequency ν1 in
HfCl62– is always slightly higher than in ZrCl62– (Table
1 and [8–12, 18]) in spite of the fact that frequencies of
M–Cl stretching vibrations for elements of the same group
of the periodic system usually decrease as the weight of a
central atom increases [19]. It also can testify to relatively
greater M–Cl bond strength in chloride complexes in case
of hafnium compounds [19, 22].
CONCLUSIONS
–
(M = Zr, Hf) in M2Cl9 groups are connected pairwise by
three halogen bridges through a common edge.
(1) Material compositions of ZrCl4 and HfCl4 fusion
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