ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2020, Vol. 65, No. 9, pp. 1398–1406. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Neorganicheskoi Khimii, 2020, Vol. 65, No. 9, pp. 1256–1264.
PHYSICOCHEMICAL ANALYSIS
OF INORGANIC SYSTEMS
Chemical Interactions in Na+,Sr2+||Cl–, 2 − (E = Mo,W)
and Na+,Sr2+||Cl–,
,
Reciprocal Systems:
2−
2−
Description and Study
I. K. Garkushina, *, A. V. Burchakova, M. A. Sukharenkoa, N. N. Verdievb, and S. N. Milova
aSamara State Technical University, Samara, 443100 Russia
bInstitute of Geothermy and Renewable Energy, Branch of the Joint Institute for High Temperatures
of the Russian Academy of Sciences, Makhachkala, 367030 Russia
*e-mail: gik49@yandex.ru
Received March 4, 2020; revised April 3, 2020; accepted April 30, 2020
Abstract—Chemical interactions of salts in the four-component reciprocal system comprised of chlorides,
molybdates, and tungstates of sodium and strontium are studied by the ion-balance method. DTA heating
curves feature exotherms due to the interaction of Na2EO4 + SrCl2 (E = Mo,W) and Na2MoO4 + Na2WO4 +
SrCl2 homogenized powdery batches. Cooling curves feature exotherms indicating the formation of exchange
2−
reaction products upon crystallization of batches from NaCl + SrEO melts in the Na+,Sr2+||Cl–,
and
EO4
4
2−
NaCl + SrMoxW1 – xO ternary reciprocal systems and in the Na+,Sr2+||Cl–,
,
2− four-component
MoO4 WO4
4
reciprocal system. Reaction products are identified by X-ray powder diffraction. The presence of double
2−
compounds Na ClMoO and Na ClWO in reaction products in the Na+,Sr2+||Cl–,
systems and the
EO4
3
4
3
4
2−
presence of Na3ClMoxW1 – xO solid solutions (ss) in the Na+,Sr2+||Cl–,
,
2−system is considered
MoO4 WO4
in terms of divergence phenom4ena.
Keywords: chemical interaction, phase reactions, ion balance method
DOI: 10.1134/S003602362009003X
INTRODUCTION
ous thermal analyzer [10, 11]. The thermo-e.m.f.
source used was a Pt–Rh/Pt thermocouple. The
accuracy of temperature determination after calibra-
tion with reference substances was 1.5°С. X-ray
powder diffraction experiments were carried out on a
DRON-2.0 diffractometer (Niβ-filtered CuKα radia-
tion) [12–14]. The precursors were weighed on a Shi-
madzu AUX 220 analytical balance. The weighed pre-
cursors were pounded with an agate mortar and a pes-
tle and then triturated with acetone; after acetone was
evaporated, a 0.1-g aliquot of the powder was placed
into a platinum microcrucible. A second crucible con-
tained an Al2O3 (analytical reagent grade) reference.
The heating rate was 10 K/min.
Alkaline-earth-metal molybdates, tungstates, and
their isomorphic mixtures are widely used as phos-
phors for producing single crystals with the aim of
using the stimulated Raman scattering (SRS) effect in
lasers [1–6]. Strontium molybdate and strontium
tungstate crystals and their solid solutions (ss) have
most technologically convenient and close-to-record
SRS characteristics. Therefore, studies of phase dia-
grams of multicomponent systems and chemical inter-
actions involving molybdates and tungstates of alka-
line-earth metals are not only of theoretical, but also
of practical interest [7, 8].
EXPERIMENTAL
THEORY
The exchange reaction
2−
2−
The Na+,Sr2+||Cl–,
four-component
MoO4 WO4
,
reciprocal system was previously studied by the con-
version method [9]. In the study reported here, we
used the following salts: specialty grade NaCl, pure
grade Na2MoO4 and Na2WO4, and analytical reagent
grade SrCl2, SrMoO4, and SrWO4. The investigation
tool was an STA 449 F3 Phoenix (Netzsch) simultane-
(1)
Na EО + SrCl = 2NaCl + SrEO E = Mo,W ,
2
4
2
4
°
is exothermic (
< 0) when
<
and
<
rCl−
= 0.181 nm,
Δr H298
rNa+ rSr2+
:
= 0.098 nm,
= 0.294 nm,
r
rNa+
rSr2+
rCl−
= 0.257 nm [15, 16].
EO24−
= 0.254 nm, and
r
r
WO24−
MoO24−
1398