Synthesis and powder X-ray diffraction analysis of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl

Article abstract of DOI:10.1023/A:1022440130213

A series of new mixed rare-earth and selenium oxychlorides with composition LnSeO₃Cl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together LnOCl and SeO₂ in sealed silica tubes. The resulting compounds were characterized by powder X-ray diffraction. The unit cell parameters of the phases were determined. Lanthanum - europium oxychlorides crystallized in the tetragonal system to give the Sillen phases analogously to tellurium compounds with the similar formula, whereas Tb-Yb and Y oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are not layered compounds.

Full text of DOI:10.1023/A:1022440130213

98
Russian Chemical Bulletin, International Edition, Vol. 52, No. 1, pp. 98—102, January, 2003
Synthesis and powder Xꢀray diffraction analysis
of new mixed rareꢀearth and selenium oxychlorides
with composition LnSeO Cl
3
D. G. Shabalin, P. S. Berdonosov, V. A. Dolgikh, H. Oppermann,c
a
bꢀ
b
P. Schmidt, and B. A. Popovkinb
c
aDepartment of Materials Science, M. V. Lomonosov Moscow State University,
Leninskie Gory, 119992 Moscow, Russian Federation.
Eꢀmail: shabalin@r450.inorg.chem.msu.ru
b
Department of Chemistry, M. V. Lomonosov Moscow State University,
Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (095) 939 0998. Eꢀmail: psberd@inorg.chem.msu.ru; dolgikh@inorg.chem.msu.ru
c
Institute of Inorganic Chemistry, Technical University of Dresden,
Mommsenstraße 13, Dꢀ01069, Dresden, Germany.*
Fax: +49 (351) 4633 7287. Eꢀmail: peer.schmidt@chemie.tuꢀdresden.de
A series of new mixed rareꢀearth and selenium oxychlorides with composition LnSeO Cl
3
(
Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together
LnOCl and SeO in sealed silica tubes. The resulting compounds were characterized by powꢀ
2
der Xꢀray diffraction. The unit cell parameters of the phases were determined. Lanthaꢀ
num—europium oxychlorides crystallized in the tetragonal system to give the Sillen phases
analogously to tellurium compounds with the similar formula, whereas Tb—Yb and Y
oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are
not layered compounds.
Key words: Sillen phases, rareꢀearth and selenium oxychlorides, powder Xꢀray diffraction
characteristics.
1
Earlier, we have synthesized a large series of bisꢀ
Dy, Ho, Er, Yb, or Y) and performing their Xꢀray diagꢀ
nostics. The data on these phases are lacking in the litꢀ
erature.
muth—tellurium and rareꢀearth metal (REM)—telluꢀ
rium oxyhalides. Many of these compounds have
nonꢀcentrosymmetrical structures. The most common
composition of the compounds, which was found in all
M O —MOHal—TeO systems, corresponds to the forꢀ
Results and Discussion
2
3
2
mula MTeO Hal, where M = Bi or any REM and Hal =
The samples synthesized in the present study occur as
pale powders (in the case of Nd and Er, as pinkish powꢀ
ders). The powder Xꢀray diffraction patterns of all anꢀ
nealed samples have no lines of the starting phases or
known phases in the Ln O —LnCl —SeO systems. Acꢀ
cording to the character of arrangement and intensities of
reflections in the powder diffraction patterns, the comꢀ
pounds under consideration can be classified into two
groups: 1) derivatives of Ln = La—Eu and 2) derivatives
of Ln = Tb—Yb and Y. Figure 2 shows the powder diffracꢀ
3
Cl, Br, or I. All phases with this composition have layered
1
structures of the Sillen phases, which are built by alterꢀ
nating double (M O ) and triple (MTe O ) fluoriteꢀlike
2
2
2
5
layers separated by the single and double layers of halide
anions (Fig. 1).
2
3
3
2
Rather recently, bismuth—selenium oxyhalides with
analogous stoichiometry BiSeO Hal (Hal = Cl or Br)
3
have been synthesized.2 However, their structures difꢀ
—4
fer from those found for the tellurium derivatives. In adꢀ
5
dition, we have prepared the SmSeO Cl phase.
tion patterns of the samples with compositions SmSeO Cl
3
3
The present study was aimed at synthesizing the
and HoSeO Cl as typical examples. The gadoliniumꢀconꢀ
3
LnSeO Cl phases (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb,
taining sample boundary to both families of oxychlorides
gives a diffraction pattern, which is similar in the arrangeꢀ
ment of lines to the family of light REMs and still has
noticeable differences (see Fig. 2). The diffraction pattern
3
*
Technishe Universität Dresden, Institut für Anorganische
Chemie, Mommsenstraße 13, Dꢀ01069, Dresden, Germany.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 93—96, January, 2003.
066ꢀ5285/03/5201ꢀ98 $25.00 © 2003 Plenum Publishing Corporation
1

New REM—Se oxychlorides LnSeO Cl
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
99
3
c
Table 1. Unit cell parameters (Å) of the LnSeO Cl compounds
3
belonging to the tetragonal (space group P4/nmm) and orthoꢀ
rhombic (Pnma) systems
[
Cl2]
Ln
a
b
c
P4/nmm
—
La
Pr
Nd
Sm
Eu
4.026(2)
3.9805(6)
3.9627(7)
3.931(2)
3.906(1)
26.56(2)
26.346(9)
26.30(2)
26.14(2)
26.09(1)
—
—
—
—
[
SmTe O ]
2 5
Pnma
7.031(2)
6.980(6)
6.910(3)
6.943(5)
6.909(4)
6.818(8)
6.896(5)
Cl
Te
Gd
Tb
Dy
Ho
Er
7.253(2)
7.244(8)
7.177(4)
7.233(6)
7.201(4)
7.140(8)
7.185(6)
8.871(4)
8.73(1)
8.721(7)
8.795(6)
8.750(4)
8.65(1)
8.73(2)
[
[
Cl]
Sm O ]
2
2
Sm
O
Yb
Y
[
Cl]
and the space group P4/nmm (Table 1). Table 2 gives the
results of indexing of the diffraction pattern of the
PrSeO Cl sample as a typical example.
3
A series of lines in the diffraction pattern of the
GdSeO Cl sample annealed at 300 °C can also be indexed
3
[
SmTe O ]
2 5
within an analogous unit cell. Apparently, the structure of
this compound corresponds to a distorted structure of
lighter REM oxychlorides. We failed to index all reflecꢀ
tions in the diffraction pattern of this sample.
The diffraction patterns of the LnSeO Cl compounds,
[
Cl2]
3
where Ln = Gd, Tb, Dy, Ho, Yb, or Y, were indexed
under the assumption of the orthorhombic system and the
Fig. 1. Fragment of the SmTeO Cl structure.
3
Table 2. Results of indexing of the powder diffraction pattern of
PrSeO Cl*
3
of the sample with composition GdSeO Cl, which was
3
annealed at 600 °C for 72 h, appeared to be similar to the
Line
d/Å
h
k
l
I/I0
diffraction patterns of the samples containing heavy REMs
Experiment Calculation
or Y (see Fig. 2). The GdSeO Cl sample was prepared in
3
connection with the fact that the heating curve, which
was obtained in the differential thermal study (evacuated
Stepanov's vessels, heating from room temperature to
1
2
3
4
5
6
7
8
9
1
11
12
1
1
1
1
1
8.81
3.626
8.78
3.626
0
1
1
1
1
1
0
1
2
2
1
2
1
2
2
2
3
0
0
0
1
1
1
0
1
0
0
0
1
1
1
0
2
0
3
3
6
0
4
6
12
9
0
3
12
3
12
6
12
0
6
60
60
100
80
10
10
10
20
40
10
10
10
10
30
10
10
10
2.9501
2.8138
2.5905
2.3693
2.1926
2.0284
1.9905
1.9419
1.9231
1.7448
1.7321
1.6509
1.4743
1.4065
1.2701
2.9491
2.8146
2.5881
2.3696
2.1955
2.0289
1.9902
1.9410
1.9224
1.7446
1.7311
1.6497
1.4745
1.4073
1.2701
–
1
6
00 °C, rate 10 deg min , Al O3 reference) of the
2
GdSeO Cl sample annealed at 300 °C, showed an exoꢀ
3
thermic effect at 565±5 °C, and this effect was not reproꢀ
duced on cooling.
The IR spectra of the samples belonging to the same
family are also very similar to each other and differ noꢀ
ticeably from the IR spectra of compounds belonging to
another family. The typical IR spectra of the samples
with compositions SmSeO Cl and HoSeO Cl are shown
0
3
4
5
6
7
3
3
in Fig. 3.
The powder diffraction patterns of the La—Euꢀconꢀ
taining compounds were indexed based on their similarity
to the diffraction patterns of the known MTeO Hal comꢀ
3
pounds assuming the tetragonal symmetry of the unit cells
* The figure of merit F(17) = 7.9.

1
00
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Shabalin et al.
I/pulse
1
1
50
00
1
2
5
0
2
0
30
40
50
60
2θ/deg
I/pulse
8
6
00
00
2
2
0
0
30
30
40
40
50
50
60
60
2θ/deg
2θ/deg
I/pulse
I/pulse
1
1
500
000
3
4
2
1
000
000
2
0
30
40
50
60
2θ/deg
Fig. 2. Xꢀray diffraction patterns of SmSeO Cl (1), GdSeO Cl (2, 3), and HoSeO Cl (4) annealed at 300 (1, 2, 4) and 600 °C (3).
3
3
3
T
space group Pnma (see Table 1). Table 3 gives the results
of indexing of the diffraction pattern of the HoSeO Cl
3
sample as an example. It should be noted that the reflecꢀ
tion with 2θ = 30.667°, d = 2.9130 Å, I/I = 63.3, which
0
was observed in the diffraction pattern of the GdSeO Cl
3
compound annealed at 600 °C, could not be indexed
within the unit cell parameters given in Table 1.
2
The results obtained in the present study provide eviꢀ
dence that all rareꢀearth metals under consideration form
compounds with composition LnSeO Cl. Most likely, the
3
structure type of these phases depends on the size of the
3
+
Ln ion. Oxychlorides LnSeO Cl containing lanthanides
3
with large ionic radii have the Bi0.97TeO Br structures
3
0.9
(
see Fig. 1). The parameter а monotonically decreases on
going from La to Eu. In the structures of this type, the
parameter а is numerically equal to the Ln—Ln distance
1
(
see Fig. 1). Hence, its change in the series under considꢀ
eration can be explained in the context of the phenomꢀ
enon of lanthanide contraction. The parameter с also
decreases on going from La to Eu. This parameter for the
Bi0.97TeO Br structures would be determined primaꢀ
3
0.9
rily by the thicknesses of the fluoriteꢀlike [Ln O ] and
2
2
[
LnSe O ] packets (see Fig. 1), which decrease with deꢀ
2 5
3
+
creasing ionic radius of Ln due to a decrease in the
Ln—O distance. This change in the parameter с can also
be accounted for by the lanthanide contraction.
6
00
400
200
ν/cm–1
Fig. 3. IR absorption spectra of SmSeO Cl (1) and HoSeO Cl (2).
3
3

New REM—Se oxychlorides LnSeO Cl
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
101
3
Table 3. Results of indexing of the powder diffraction pattern of
The aboveꢀmentioned change in the structure type in
HoSeO Cl*
3
the LnSeO Cl series at Ln = Gd agrees with the general
3
tendency for a change in the properties of REM derivaꢀ
tives, viz., with the existence of the soꢀcalled "gadolinium
break."
Line
d/Å
h
k
l
I/I0
Experiment Calculation
When this study was being prepared for publicaꢀ
tion, the structure of the holmium—tellurium oxychloꢀ
1
2
3
4
5
6
7
8
9
5.6290
4.4123
3.7685
3.6073
3.4830
3.2137
3.0175
2.9597
2.7166
5.5863
4.3975
3.7575
3.6163
3.4713
3.2073
3.0132
2.9485
2.7247
1
0
1
2
0
2
2
1
0
1
2
1
2
3
0
1
1
1
1
2
2
2
2
1
0
1
0
4
2
3
3
4
1
1
2
4
4
1
1
0
0
0
0
2
1
1
2
2
0
1
2
0
1
0
2
3
0
1
3
2
3
3
3
4
0
1
0
2
2
3
2
4
3
4
0
1
4
0
1
2
2
0
0
0
1
1
2
3
2
2
3
1
4
3
1
4
4
0
3
1
2
3
0
5
5
2
4
3
1
1
2
4
1
3
3
3
6
73.5
18.3
59.1
2.3
100.0
17.3
36.2
7.0
ride HoTeO Cl was established (orthorhombic system,
3
space group Pnma; a = 7.3025(5), b = 6.9654(5), c =
6
9
.0518(7) Å; Z = 4) and reported. The unit cell paramꢀ
6
eters published in the cited study are very close to those
determined in our study for the LnSeO Cl compounds
3
with end members of the REM series taking into considꢀ
eration that the radius of Se is smaller than that of Te.
Hence, it can be assumed that the structures of the comꢀ
18.2
2
.7170
1
1
1
1
0
1
2
3
2.5917
2.5439
2.2758
2.2046
2.5913
2.5498
2.2773
2.2048
21.2
15.3
5.6
pounds under consideration are similar to the HoTeO Cl
3
structure.
20.9
2
.1988
2.1395
.1380
Experimental
1
4
2.1394
13.4
2
The present study was carried out with the use of the
oxychlorides LnOCl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er,
Ho, Yb, or Y) and selenium dioxide.
1
1
1
1
5
6
7
8
2.0989
2.0161
1.9489
1.9013
2.1037
2.0133
1.9493
1.9042
3.1
7.0
5.1
4.3
Oxychlorides of the aboveꢀmentioned REMs were prepared
7
according to a procedure described earlier by pyrohydrolysis of
1
.9031
the corresponding REM trichloride hexahydrates at 400—500 °C
for 2—4 h. Some rareꢀearth trichloride hexahydrates were comꢀ
mercially available reagents (highꢀpurity grade) and the remainꢀ
ing reagents were prepared by dissolution of oxides of the correꢀ
sponding lanthanides in concentrated HCl followed by conꢀ
centration of the solutions on a sand bath until crystallization
started.
1
2
2
2
9
0
1
2
1.7818
1.7606
1.7345
1.7077
1.7820
1.7618
1.7357
1.7092
5.1
2.7
4.8
3.0
1
.7051
2
2
2
3
4
5
1.6707
1.6537
1.6385
1.6723
1.6523
1.6409
2.0
3.2
5.9
Selenium dioxide was synthesized according to a known
8
procedure by oxidation on heating of powdered selenium (highꢀ
1
.6402
1.5776
.5757
purity grade) in a flow reactor under a stream of air and nitrogen
oxides, which were generated by thermal decomposition of
Pb(NO3)2 at 400—450 °C. White SeO2 crystals, which were
condensed in the cold zone of the reactor, were transferred into
a tube. The tube was sealed and placed in a dry box, where all
2
6
1.5780
3.7
1
2
2
7
8
1.5562
1.5379
1.5567
1.5406
2.9
1.3
1
.5390
subsequent operations with SeO were carried out.
2
2
3
3
9
0
1
1.5028
1.4625
1.4364
1.5025
1.4627
1.4366
1.2
1.6
2.5
The products thus obtained were identified by powder Xꢀray
diffraction analysis (Stoe diffractometer, Stadiꢀp, CuꢀKα1 raꢀ
diation) based on the data from the JCPDS PDFꢀ2 database.
The LnSeO Cl sample was synthesized by solidꢀphase anꢀ
nealing (300±5 °C, 240 h) of carefully ground equimolar mixꢀ
*
The figure of merit F(31) = 7.8.
3
tures of REM oxychlorides and SeO2 in evacuated (residual
pressure was 1•10–2 Pa) silica tubes.
We believe that this factor is also responsible for a
decrease in the unit cell parameters of the orthorhombic
Xꢀray diffraction and IR spectroscopic diagnostics. Xꢀray difꢀ
phases LnSeO Cl on going from Gd to Yb.
fraction diagnostics of the annealing products was carried out on
3
a Stoe diffractometer (Stadiꢀp, CuꢀKα radiation) and a Guinier
Apparently, gadolinium—selenium oxychloride exists
on the boundary of stability of two structure types and can
occur as two modifications. The orthorhombic modificaꢀ
tion is stable at high temperatures (600 °C), whereas
1
camera (Enraf—Nonius, Delft) using the photographic method
(
germanium as the internal standard). The Xꢀray diffraction
POW
patterns were processed with the use of the WinX
program
package (Stoe&CIE GmbH computer software). The Guinier
patterns were measured on an IZAꢀ2 comparator and processed
with the use of the Powder2 program package.
The IR spectra were recorded on a Perkin—Elmer
FTIRꢀ1720 instrument (as Nujol mulls).
the phase with the distorted MTeO Hal structure is
3
formed under the conditions of lowꢀtemperature annealꢀ
ing (300 °C). Apparently, the latter phase can be assigned
to the layered Sillen phases.

1
02
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Shabalin et al.
We thank L. N. Reshetova for help in recording the IR
spectra.
4. H. Oppermann, P. Schmidt, M. ZhangꢀPreβe, Dao Quoc
Huong, R. Kucharkowski, B. A. Popovkin, S. A. Ibragimov,
and V. A. Dolgikh, Z. Anorg. Allg. Chem., 2002, 628, 91.
5. H. Oppermann, Dao Quoc Huong, M. ZhangꢀPreβe,
P. Schmidt, B. A. Popovkin, P. S. Berdonosov, and V. A.
Dolgikh, Z. Anorg. Allg. Chem., 2002, 628, 891.
This study was financially supported by the Russian
Foundation for Basic Research and the German Research
Foundation (DFG, Deutsche Forschungsgemeinschaft;
RFBRꢀDFG Project No. 01ꢀ03ꢀ04002).
6
7
8
. S. F. Meier and Th. Schleid, Z. Anorg. Allg. Chem., 2002,
28, 526.
. G. Brauer, Handbuch der Präparativen Anorganischen Chemie,
Ferdinand Enke Verlag, Stuttgart, 1975.
. Yu. V. Karyakin and I. I. Angelov, Chistye khimicheskie
reaktivy. Rukovodstvo po prigotovleniyu neorganicheskikh
reaktivov i preparatov v laboratornykh usloviyakh [Pure Chemiꢀ
cal Reagents. Laboratory Manual on Preparation of Inorganic
Reagents], Khimiya, Moscow, 1974, 56 (in Russian).
6
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2
3
Received May 14, 2002;
in revised form October 4, 2002