Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1035 1037. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
2005, pp. 1057 1059.
Original Russian Text Copyright
2005 by Basiev, Batyrev, Voronov, Konyushkin, Kuznetsov, Osiko, Samartsev, Samoilova, Fedorov.
INORGANIC SYNTHESIS
AND INDUSTRIAL INORGANIC CHEMISTRY
Hydration of Strontium Chloride and Rare-Earth
Element Oxychlorides
T. T. Basiev, N. I. Batyrev, V. V. Voronov, V. A. Konyushkin, S. V. Kuznetsov,
V. V. Osiko, A. M. Samartsev, E. B. Samoilova, and P. P. Fedorov
Scientific Center of Laser Materials and Technologies, Institute of General Physics,
Russian Academy of Sciences, Moscow, Russia
Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow, Russia
Received November 15, 2004
Abstract Hydration and dehydration (on calcination) of SrCl2, YOCl, and HoOCl powders were studied.
Single-crystal chloride materials are of interest for
photonics owing to their transparence in the IR range
and a soft photon spectrum. The main problem in
both growing the crystals and working with them is
their hydration. In particular, chlorides of rare-earth
elements are very hygroscopic; hydrated rare-earth
chlorides are readily hydrolyzed on heating [1 6].
This substantially complicates the use of such materi-
als, though the spectroscopic characteristics, e.g., of
We prepared strontium chloride by the reaction
SrCO3 + 2NH4Cl = SrCl2 + H2O + CO2 + 2NH3 . (1)
We used a fourfold excess of NH Cl. The reaction
4
was carried out in an alundum crucible at 150 350 C
for 6 h. The yield of SrCl was 99%. The resulting
2
SrCl had a cubic fluorite-type lattice with a =
2
6.977 , which agrees with the published data (PDF
card no. 38-0496). On exposure to air, the sample
weight continuously increased; the process gradually
decelerated with time (Fig. 1). The increase in the
substance weight in the first hour was 7%. The in-
crease in the sample weight was accompanied by
3+
LaCl : R single crystals are highly promising [7].
3
Among matrices resistant to moisture are PbCl and
2
KPb Cl [8 10].
2
5
In this study we examined the hydration of SrCl
2
powders and also of oxychlorides of rare-earth ele-
ments. Strontium chloride crystallizing in a cubic
lattice of the fluorite type has a high isomorphous
capacity with respect to chlorides of rare-earth ele-
changes in its X-ray pattern. Along with the SrCl
lines, an additional set of reflections appeared, and
their intensities rapidly increased, whereas the lines of
2
SrCl weakened (Fig. 2). Analysis of the pattern using
2
ments [11]. Properties of SrCl single crystals and of
2
the PDF database revealed mixture of mono-, di-, and
Sr R Cl
solid solutions have been studied re-
1
x
x
2 +x
hexahydrates of SrCl . The final hydration product
2
peatedly [12 14]. Oxychlorides of rare-earth elements
are more resistant to moisture than the chlorides [15].
Therefore they could be a convenient form for intro-
ducing dopants.
was SrCl 6H O. On calcination of strontium chlor-
2
2
ide hexahydrate at 350 C for 2 h, the weight loss cor-
responded to complete dehydration. The subsequent
We used ultrapure 7 4 grade SrCO , chemically
3
m, g
pure grade ammonium chloride NH Cl, and chemical-
4
ly pure grade hydrates of rare-earth elements RCl
3
6H O as starting substances. The initial chemicals
2
were characterized by X-ray diffraction. The X-ray
phase analysis was carried out on a DRON-2 diffrac-
tometer (CuK radiation, focusing monochromator
from pyrolytic graphite). We recorded variations in
sample weights on an Acculab V-200 electron balance.
The humidity was measured with a psychrometer.
The hydration was carried out at 19 2 C and the rela-
tive humidity of 38 5%.
t, h
Fig. 1. Kinetics of SrCl hydration. ( m) Change in the
2
weight of the sample and (t) time.
1070-4272/05/7807-1035 2005 Pleiades Publishing, Inc.