SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS
This work reports on the preparation and characterization of Sr2+-doped Ba7Nb4MoO20 powders prepared by a solid-state synthesis as promising materials for solid oxide fuel cells. The influence of synthesis parameters and strontium content (x = 0; 0.05; 0.10; 0.15; 0.20) on the phase composition and...
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| Дата: | 2022 |
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| Формат: | Стаття |
| Мова: | Англійська |
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V.I.Vernadsky Institute of General and Inorganic Chemistry
2022
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Репозитарії
Ukrainian Chemistry Journal| _version_ | 1871465819051917312 |
|---|---|
| author | Bezdorozhev, Oleksii Solodkyi, Ievgen Ostroverkh, Anna Morozov, Igor Ostroverkh, Yevhenii Solonin, Yuriy |
| author_facet | Bezdorozhev, Oleksii Solodkyi, Ievgen Ostroverkh, Anna Morozov, Igor Ostroverkh, Yevhenii Solonin, Yuriy |
| author_institution_txt_mv | [
{
"author": "Oleksii Bezdorozhev",
"institution": "Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3, 03142, Kyiv, Ukraine"
},
{
"author": "Ievgen Solodkyi",
"institution": "National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Peremogy ave. 37, 03056, Kyiv, Ukraine"
},
{
"author": "Anna Ostroverkh",
"institution": "Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3, 03142, Kyiv, Ukraine"
},
{
"author": "Igor Morozov",
"institution": "Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3, 03142, Kyiv, Ukraine"
},
{
"author": "Yevhenii Ostroverkh",
"institution": "Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3, 03142, Kyiv, Ukraine"
},
{
"author": "Yuriy Solonin",
"institution": "Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3, 03142, Kyiv, Ukraine"
}
] |
| author_sort | Bezdorozhev, Oleksii |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:49Z |
| description | This work reports on the preparation and characterization of Sr2+-doped Ba7Nb4MoO20 powders prepared by a solid-state synthesis as promising materials for solid oxide fuel cells. The influence of synthesis parameters and strontium content (x = 0; 0.05; 0.10; 0.15; 0.20) on the phase composition and properties of (Ba1-xSrx)7Nb4MoO20 powders was studied. The results of the phase analysis show that (Ba1-xSrx)7Nb4MoO20 (x = 0; 0.05; 0.10) powders with a minimum amount of secondary phases can be obtained after at least three repeated synthesis cycles at 1060–1080 оС for 10 h. According to the laser diffraction analysis, the synthesized powders comprise particles with a polydisperse size distribution spreading from 0.05 μm to 12 μm and average particle size of 2.1 μm. Electron microscopy observations support these findings and demonstrate that the particles and their aggregates have rounded irregular shape. Moreover, it was found that the morphology and particle size of the powder does not depend on the strontium content. Doping (Ba1-xSrx)7Nb4MoO20 with 15 mol.% and 20 mol.% Sr2+ leads to the formation of a significant amount of secondary phases due to exceeding the solubility limit of strontium, thus making these compositions unsuitable for use in solid oxide fuel cells. |
| doi_str_mv | 10.33609/2708-129X.88.04.2022.63-78 |
| first_indexed | 2025-09-24T17:43:44Z |
| format | Article |
| fulltext |
63
UDC 621.762.242+661.8...22 doi: 10.33609/2708-129X.88.04.2022.63-78
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20
POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS
O. V. Bezdorozhev1,*, I. V. Solodkyi2, A. S. Ostroverkh1, I. A. Morozov1,
Y. M. Ostroverkh1, Yu. M. Solonin1
1Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Krzhizhanovsky str. 3,
03142, Kyiv, Ukraine
2National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Peremogy ave.
37, 03056, Kyiv, Ukraine
*e-mail: oleksii.bezdorozhev@gmail.com
This work reports on the preparation and characterization of Sr2+-doped Ba7Nb4MoO20
powders prepared by a solid-state synthesis as promising materials for solid oxide fuel cells.
The influence of synthesis parameters and strontium content (x = 0; 0.05; 0.10; 0.15; 0.20)
on the phase composition and properties of (Ba1-xSrx)7Nb4MoO20 powders was studied. The
results of the phase analysis show that (Ba1-xSrx)7Nb4MoO20 (x = 0; 0.05; 0.10) powders with a
minimum amount of secondary phases can be obtained after at least three repeated synthesis
cycles at 1060–1080 оС for 10 h. According to the laser diffraction analysis, the synthesized
powders comprise particles with a polydisperse size distribution spreading from 0.05 μm to
12 μm and average particle size of 2.1 μm. Electron microscopy observations support these
findings and demonstrate that the particles and their aggregates have rounded irregular shape.
Moreover, it was found that the morphology and particle size of the powder does not depend
on the strontium content. Doping (Ba1-xSrx)7Nb4MoO20 with 15 mol.% and 20 mol.% Sr2+ leads
to the formation of a significant amount of secondary phases due to exceeding the solubility
limit of strontium, thus making these compositions unsuitable for use in solid oxide fuel cells.
Keywords: solid-state synthesis, perovskite, Ba7Nb4MoO20, powder, electrolyte.
INTRODUCTION
In recent years, the world is increasingly fo-
cused on hydrogen energy as one of the clean
energy sources [1, 2]. The use of hydrogen will
have a positive impact on environmental, ener-
gy security and economic development issues
[3]. Hydrogen can be obtained by electrolysis
of water using electricity produced from excess
renewable energy [4, 5]. The produced hydro-
gen can be burned to generate electricity and
heat using fuel cells, which are more efficient
than combustion engines [6, 7].
Fuel cells (FCs) are electrochemical de-
vices that can convert the chemical energy
64 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
of a fuel directly into electrical and thermal
energy [8]. The main advantages of FCs are
high efficiency (up to 50%) [9], low level of
pollutants and noise emissions, modularity
and compact design, which allows easy and
quick assemble of power plants with different
capacities within one technology [8]. Among
many types of FCs, the most promising for
electrochemical oxidation of hydrogen are
solid oxide fuel cells (SOFCs) with a ceramic
oxide electrolyte. SOFCs can be divided into
two types with respect to the charge trans-
fer mechanism through a dense electrolyte:
oxygen-ion-conducting (O2--SOFCs) and
proton-conducting (H+-SOFCs). The main
advantage of O2--SOFCs is their flexibility in
terms of using different types of gaseous fuel
that is oxidized at the anode [10]. While H+-
SOFCs have higher energy conversion effi-
ciency (up to 60%) due to lower activation en-
ergy of proton conductivity (0.3–0.6 eV) com-
pared to that of ionic conductivity (0.8–1.1
eV) [11]. In addition, water is formed at the
cathode during the operation of H+-SOFCs,
and therefore the fuel does not mix with the
products of its oxidation leading to more ef-
ficient fuel utilization. High efficiency at low
temperatures (500–600 oC) reduces the re-
quirements for other SOFCs components and
significantly decreases the rate of their deg-
radation. These advantages provide 27–37%
lower cost for production of H+-SOFC stacks
with an operating temperature of 550 oC com-
pared to O2--SOFCs operating at 800 oC [12].
Solid solutions of BaZrO3 and BaCeO3 with
the perovskite-type ABO3 structure are the
most widely used electrolytes for H+-SOFCs
[13–16]. However, the need for high sintering
temperatures (up to 1600 oC) [17] and alloying
with rare earth oxides encourage the search for
new, more technological and cheaper materials
with better functional properties.
High proton and oxide ion conductivity in
Ba7Nb4MoO20 compound with a disordered
hexagonal perovskite structure has recently
been discovered [18, 19]. This perovskite has
high oxide ion conductivity in dry oxygen envi-
ronment and proton conductivity in a humidi-
fied or reducing atmosphere. For example, the
bulk conductivity in humidified air at 510 oC
is about twice as high (4 mS/cm) compared to
the conductivity in dry air (1.9 mS/cm). Note
that the bulk conductivity of Ba7Nb4MoO20
in dry oxygen is significantly higher than
that for 8YSZ and is comparable with that of
La0.8Sr0.2Ga0.83Mg0.17O2.815, whereas in humidi-
fied air (pH2O ∼0.021 atm) the proton conduc-
tivity of Ba7Nb4MoO20 is close to that of barium
cerates. Fop et al. [20] also demonstrated that
the positional oxide ion disorder generated by
the close proximity of available oxygen sites
due to the particular topology of the palmierite
layers in hydrated Ba7Nb4MoO20 contributes to
the creation of a frustrated proton sublattice
with high proton mobility and low energy dif-
fusion pathways. Ba7Nb4MoO20 also has low
sintering temperature (up to 1200 oC) and rela-
tively high chemical resistance to CO2 [18].
Two recent papers [18, 19] have noted that
the properties of Ba7Nb4MoO20 can be im-
proved by doping, in this regard we proposed
the synthesis of (Ba1-xSrx)7Nb4MoO20 (x = 0.05;
0.10; 0.15; 0.20), where part of Ba atoms is re-
placed by Sr atoms. The choice of strontium as
an alloying additive is due to its similar chem-
ical properties and ionic radius (1.39 Å for
Sr2+) to barium (1.49 Å for Ba2+) [21] that will
provide partial replacement of barium atoms
without destroying the crystal lattice of the
perovskite.
65https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
Regarding the synthesis of Ba7Nb4MoO20,
it should be noted that this issue is almost not
studied in the available literature. The first re-
port on the synthesis and crystal structure of
Ba7Nb4MoO20 was made by Garcia-Gonzalez
et al. [22], who synthesized it by solid-state
reaction of BaCO3, Nb2O5, and MoO3 at
1300 oC for 72 hours. Fop et al. [18] reported
that a single-phase powder can be obtained
after repeated annealing at 1050 oC, while the
synthesis at 1100–1150 oC leads to the for-
mation of phases other than Ba7Nb4MoO20.
Whereas in the paper [19], repeated anneal-
ing at 900 oC for 10–12 hours was carried out
to synthesize Ba7Nb4MoO20-based materials.
Taking into account the discrepancies not-
ed above, as well as the fact that strontium
carbonate has a higher melting point (tm =
1497 oC) than barium carbonate (tm = 811 oC)
[23], we tailored the synthesis parameters and
then synthesized (Ba1-xSrx)7Nb4MoO20 with
various strontium content (x = 0; 0.05; 0.10;
0.15; 0.20). The phase composition, particles
size and morphology of the obtained powders
were studied.
EXPERIMENT AND DISCUSSION OF
THE RESULTS
Solid-state synthesis was used to ob-
tain powders with nominal compositions
of (Ba1-хSrx)7Nb4MoO20, х = 0.05; 0.10; 0.15;
0.20. Barium carbonate (BaCO3, ≥99%, Carl
Roth GmbH + Co. KG), strontium carbonate
(SrCO3, 99%, Alfa Aesar), niobium(V) oxide
(Nb2O5, 99.5%, ChemPur Feinchemikalien
und Forschungsbedarf GmbH), and molyb-
denum(VI) oxide (MoO3, ≥99.8%, Carl Roth
GmbH + Co. KG) were used as starting ma-
terials. The required amount of materials was
mixed and ground in a porcelain mortar. The
resulting mechanical mixture was sieved and
packed down tightly into the crucible by tamp-
ing with a glass rod. The solid-state synthesis of
(Ba1-хSrx)7Nb4MoO20 powders was performed
in an air muffle furnace at temperatures of
1000–1100 oC (step 20 oC) to determine the
best reaction conditions for obtaining pow-
ders with the maximum concentration of the
required phase. The duration of each synthesis
was 10 h, and the number of repeated synthe-
sis operations under the same conditions was
varied from two to four in order to optimize
the synthesis process as well. The heating rate
to the dwell temperature was 8 oC/min, while
cooling was allowed to take place naturally. Af-
ter each annealing the powders were addition-
ally grinded and mixed.
The effect of synthesis temperature and
strontium content on the phase composition of
powders was investigated by X-ray diffraction
method using Rigaku Ultima IV diffractometer
(Rigaku Co. Ltd., Japan). The diffractograms
were recorded using continuous scanning with
a step of 0.05o or with a counting time of 4 s per
step at U = 30 kV, I = 30 mA with monochro-
matic Cu Kα radiation. Phase analysis was per-
formed using the JCPDS database and PDXL2
v. 2.0.3.0 software.
The average crystallite size was calculat-
ed using the Scherrer formula [24] from the
two most intense diffraction peaks at ~27.8o
and ~30.5o corresponding to (014) and (110)
planes of Ba7Nb4MoO20 structure, respectively:
D = 0.89λ/βcosθ , (1)
where D is the crystallite size, λ is the X-ray
wavelength of 1.5406 Å, θ is Bragg diffraction
angle, and β is the full wide of half maximum
of the XRD peak.
66 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
Dislocation density was defined by relation
[25]:
δ = 1/D2. (2)
where δ is the dislocation density and D is the
crystallite size.
Lattice strain was calculated by using the
following equation [25]:
ε = β/4tanθ, (3)
where ε is the strain and β is the full wide of
half maximum of the XRD peak.
The particle size distribution of the powders
was measured by Bettersizer S3 Plus (Better-
size Instruments Ltd., China), which deter-
mine the angular variation in intensity of light
scattered as a laser beam passes through a dis-
persed particulate sample. Distilled water was
used as the dispersing medium. An ultrasonic
actuator built into the device was used to de-
stroy weak agglomerates. The Fraunhofer eva
luation model was applied to process the raw
data using associated software.
Electron microscopic studies of the ob-
tained powders were performed on a scanning
electron microscope (SEM) Axia ChemiSEM
(Thermo Fisher Scientific Inc., USA).
The synthesized (Ba1-хSrx)7Nb4MoO20 pow-
ders with a nominal content of Sr2+ equal to
5 mol.%, 10 mol.%, 15 mol.%, and 20 mol.% are
denoted as BS5NMO, BS10NMO, BS15NMO,
and BS20NMO, respectively for convenience.
Chemical reactions between carbonates and
metal oxides take place during the heating and
holding processes at the annealing temperature
of the powder mixture. Due to the low melting
point of barium carbonate (tm = 811 оС) and
molybdenum oxide (tm = 802 оС) [23], the
synthesis occurs through the formation of a li
quid phase, which accelerates the processes of
homogenization and phase formation. After
some period of time, the synthesis proceeds in
the solid phase due to the formation of more
refractory oxides [18], which finally form
Ba7Nb4MoO20 perovskite at optimal solid-state
reaction conditions.
To determine the optimal temperature for
solid-state reaction, a powder mixture with a
nominal composition of (Ba0.9Sr0.1)7Nb4MoO20
was selected as a representative sample, the
phase composition of which was investigated
within a 2θ range of 23–33o, where the main
peaks of the formed phases are located [18,
19]. Fig. 1 shows XRD patterns of BS10NMO
powder after three annealing cycles for 10 h at
1000 oC, 1020 oC, 1040 oC, 1060 oC, 1080 oC,
and 1100 oC. According to Fig. 1a, the main
phase of the powder after synthesis at 1000 oC
is a solid solution of strontium in Ba7Nb4MoO20
(ICDD No. 00-051-0484), there are also two
secondary phases, namely, BaMoO4 (ICDD
No. 00-029-0193) and Ba4SrNb4O15 (ICDD
No. 00-054-1174). The relative intensity of
Ba4SrNb4O15 phase is high, indicating its high
concentration possibly due to the incomplete
chemical reaction at low synthesis tempera-
ture. While the amount of BaMoO4 phase is
very low as indicated by the intensity of the
main peak (Fig. 1a). The formation of these
phases is possible by the following chemical
reactions (4) – (6):
7(Ba1-хSrх)CO3 + 2Nb2O5 + MoO3 →
(Ba1-хSrх)7Nb4MoO20 + 7CO2↑ , (4)
BaCO3 + MoO3 → BaMoO4 + CO2↑, (5)
4BaCO3 + SrCO3 + 2Nb2O5 →
Ba4SrNb4O15 + 5CO2↑. (6)
67https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
Fig. 1. XRD patterns of BS10NMO powder after sythesis at (a) 1000 оС, (b) 1020 оС, (c) 1040 оС,
(d) 1060 оС, (e) 1080 оС, and (f) 1100 оС. Marked peaks: ▲ – (Ba0,9Sr0,1)7Nb4MoO20; ■ – BaMoO4; ● –
Ba4SrNb4O15; ♦ – Ba6Nb3O13.5.
Fig. 1. XRD patterns of BS10NMO powder after sythesis at (a) 1000 оС, (b) 1020 оС, (c) 1040 оС,
(d) 1060 оС, (e) 1080 оС, and (f) 1100 оС. Marked peaks: ▲ – (Ba0,9Sr0,1)7Nb4MoO20; ■ – BaMoO4;
● – Ba4SrNb4O15; ♦ – Ba6Nb3O13.5.
When the synthesis temperature was increased to 1020 oC (Fig. 1b), the phase composition
of the powder did not change qualitatively, but the diffraction pattern showed a slight increase in
the intensity of BaMoO4 peaks and the opposite for Ba4SrNb4O15 peaks. This indicates that the
amount of BaMoO4 and Ba4SrNb4O15 is slightly increased and decreased, respectively. A further
increase in the synthesis temperature to 1040 оС (Fig. 1c) led to an increase in the intensity of the
main phase peaks, while the intensities of BaMoO4 and Ba4SrNb4O15 peaks decreased, which is
accompanied by the disappearance of less intense BaMoO4 peak at 2θ = ~32.1о. These results
indicate that the chemical reaction (4) proceeds more quickly with increasing synthesis temperature.
At the synthesis temperature of 1060 oC (Fig. 1d), the tendency of reducing the intensities of
secondary phases still continues. As a result, the BaMoO4 phase disappeared completely, and the
intensity of Ba4SrNb4O15 peaks decreased by about a quarter. However, the diffraction pattern
shows a peak at 2θ = 29.5o, which most likely belongs to Ba6Nb3O13.5 (ICDD No. 00-035-0933).
This phase has two main most intense peaks, which are located at 2θ = 27.51o and 29.55o. The peak
at 27.51o is not observed, apparently due to its lower intensity in this case. The formation of
Ba6Nb3O13.5 is most likely due to the inhomogeneous distribution of the starting materials in the
mixture and/or incomplete solid-state synthesis reactions [18]. It should be noted that the content of
Ba6Nb3O13.5 phase in the obtained powder is insignificant.
When the synthesis temperature was in-
creased to 1020 oC (Fig. 1b), the phase com-
position of the powder did not change quali
tatively, but the diffraction pattern showed
a slight increase in the intensity of BaMoO4
peaks and the opposite for Ba4SrNb4O15 peaks.
This indicates that the amount of BaMoO4
and Ba4SrNb4O15 is slightly increased and de-
creased, respectively. A further increase in
the synthesis temperature to 1040 оС (Fig. 1c)
led to an increase in the intensity of the main
phase peaks, while the intensities of BaMoO4
and Ba4SrNb4O15 peaks decreased, which is ac-
companied by the disappearance of less intense
BaMoO4 peak at 2θ = ~32.1о. These results in-
dicate that the chemical reaction (4) proceeds
more quickly with increasing synthesis tem-
perature.
At the synthesis temperature of 1060 oC
(Fig. 1d), the tendency of reducing the inten-
sities of secondary phases still continues. As a
result, the BaMoO4 phase disappeared com-
pletely, and the intensity of Ba4SrNb4O15 peaks
decreased by about a quarter. However, the
diffraction pattern shows a peak at 2θ = 29.5o,
which most likely belongs to Ba6Nb3O13.5 (ICDD
No. 00-035-0933). This phase has two main
most intense peaks, which are located at 2θ =
27.51o and 29.55o. The peak at 27.51o is not ob-
served, apparently due to its lower intensity in
this case. The formation of Ba6Nb3O13.5 is most
likely due to the inhomogeneous distribution
68 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
of the starting materials in the mixture and/
or incomplete solid-state synthesis reactions
[18]. It should be noted that the content of
Ba6Nb3O13.5 phase in the obtained powder is
insignificant.
Increasing the synthesis temperature to
1080 oC under other identical conditions (triple
annealing for 10 h) resulted in the powder that
in addition to the main phase, contains only
one secondary phase, namely Ba4SrNb4O15 (see
Fig. 1e). As could be suggested from the rela-
tive intensity of Ba4SrNb4O15 peaks (Fig. 1e),
the amount of this phase is low in comparison
with the samples obtained at 1000-1040 oC and
remains almost the same as after synthesis at
1060 oC (Fig. 1d).
When the synthesis temperature was in-
creased further to 1100 oC (Fig. 1f), BaMoO4
formed and the relative intensity of Ba4SrN-
b4O15 phase increased, indicating its higher
content in the synthesized powder. The most
probable reason for this is the decomposi-
tion of (Ba0.9Sr0.1)7Nb4MoO20 to Ba4SrNb4O15
and BaMoO4 due to the low thermal stability
of (Ba0.9Sr0.1)7Nb4MoO20 at high temperatures
[18] and the evaporation of barium oxide [26,
27], according to the chemical reaction (7):
(Ba1-xSrx)7Nb4MoO20 →
Ba4-xSrxNb4O15 + Ba1-xMoO4 + BaO↑. (7)
Thus, according to the obtained XRD re-
sults, the optimal temperature interval for
solid-state synthesis of (Ba1-xSrx)7Nb4MoO20 is
1060–1080 оС that provides a minimum con-
centration of secondary phases in the powder.
In the case of solid-state synthesis, it is
common that the intermediates of the reac-
tion can be located in different parts of the
volume of the powder mixture and have dif-
ferent reactivity, as a result the efficiency of
further interaction in the system is signifi-
cantly reduced. Therefore, in order to achieve
homogeneous phase chemistry, it is necessary
to further activate the reactivity in the system,
which can be done by repeated procedures of
grinding and mixing the reaction products,
followed by prolonged annealing [18, 19,
28, 29].
Fig. 2. XRD patterns of BS10NMO powder after (a) two, (b) three, and (c) four repeated
synthesis cycles at 1080 оС for 10 h. Marked peaks: ▲ – (Ba0,9Sr0,1)7Nb4MoO20; ■ – BaMoO4;
● – Ba4SrNb4O15.
Increasing the synthesis temperature to 1080 oC under other identical conditions (triple
annealing for 10 h) resulted in the powder that in addition to the main phase, contains only one
secondary phase, namely Ba4SrNb4O15 (see Fig. 1e). As could be suggested from the relative
intensity of Ba4SrNb4O15 peaks (Fig. 1e), the amount of this phase is low in comparison with the
samples obtained at 1000-1040 oC and remains almost the same as after synthesis at 1060 oC (Fig.
1d).
When the synthesis temperature was increased further to 1100 oC (Fig. 1f), BaMoO4 formed
and the relative intensity of Ba4SrNb4O15 phase increased, indicating its higher content in the
synthesized powder. The most probable reason for this is the decomposition of
(Ba0.9Sr0.1)7Nb4MoO20 to Ba4SrNb4O15 and BaMoO4 due to the low thermal stability of
(Ba0.9Sr0.1)7Nb4MoO20 at high temperatures [18] and the evaporation of barium oxide [26, 27],
according to the chemical reaction (7):
(Ba1-xSrx)7Nb4MoO20 → Ba4-xSrxNb4O15 + Ba1-xMoO4 + BaO↑. (7)
Thus, according to the obtained XRD results, the optimal temperature interval for solid-state
synthesis of (Ba1-xSrx)7Nb4MoO20 is 1060–1080 оС that provides a minimum concentration of
secondary phases in the powder.
In the case of solid-state synthesis, it is common that the intermediates of the reaction can be
located in different parts of the volume of the powder mixture and have different reactivity, as a
result the efficiency of further interaction in the system is significantly reduced. Therefore, in order
to achieve homogeneous phase chemistry, it is necessary to further activate the reactivity in the
system, which can be done by repeated procedures of grinding and mixing the reaction products,
followed by prolonged annealing [18, 19, 28, 29].
Fig. 2. XRD patterns of BS10NMO powder after (a) two, (b) three, and (c) four repeated synthesis
cycles at 1080 оС for 10 h. Marked peaks: ▲ – (Ba0,9Sr0,1)7Nb4MoO20; ■ – BaMoO4; ● –
Ba4SrNb4O15.
69https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
The XRD pattern in Fig. 2a indicates that
double annealing at 1080 оС for 10 h is not
enough to obtain pure BS10NMO powder. Al-
though the main phase is (Ba1-xSrx)7Nb4MoO20,
there are still significant amounts of residual
phases such as BaMoO4 and Ba4SrNb4O15. After
triple synthesis processes, the concentration of
Ba4SrNb4O15 notably reduced, while BaMoO4
phase disappeared (Fig. 2b). The obtained
powder was then additionally subjected to the
synthesis procedure in order to eliminate un-
wanted phases. However, as can be seen from
Fig. 2c, the phase composition and intensity of
the peaks remained much the same indicating
that the reaction closely approached its ther-
modynamic equilibrium and further repeated
annealing can be considered as ineffective [29].
Thus, under the applied synthesis conditions,
the solid-state synthesis process should be re-
peated not less than three times in order to
obtain (Ba1-xSrx)7Nb4MoO20 perovskite with a
small amount of secondary phases.
Using the above-established optimized syn-
thesis parameters we carried out solid-state
synthesis of a series of (Ba1-xSrx)7Nb4MoO20
(x = 0; 0.05; 0.10; 0.15; 0.20) powders and stud-
ied their XRD structural parameters.
According to the XRD pattern shown
in Fig. 3a, the powder without the stron-
tium additive contains two phases, namely
Ba7Nb4MoO20 and Ba5Nb4O15, after triple an-
nealing at 1060 oC for 10 h. From the ratio of
peaks’ intensity in Fig. 3a, it can be suggested
that the amount of Ba5Nb4O15 phase is small.
In the case of BS5NMO powder (Fig. 3b), it
can be seen that except the peaks of the main
phase (solid solution of Sr in Ba7Nb4MoO20),
there are other peaks which belong to
Ba4SrNb4O15 and Ba6Nb3O13.5 phases. The small
intensity of the peaks of Ba6Nb3O13.5 indicates
that the amount of this phase is very small, while
the amount of Ba4SrNb4O15 remained almost
the same compared to that of Ba5Nb4O15 phase
in the powder without strontium additive.
To synthesize (Ba1-xSrx)7Nb4MoO20 with
10–20 mol.% Sr2+, the temperature of multiple
annealing was increased to 1080 oC in order to
accelerate the diffusion processes due to the
increase in the powder mixture of more refrac-
tory SrCO3 (tm = 1497 oC) compared to BaCO3
(tm = 811 oC) [23]. The XRD pattern of BS10N-
MO powder in Fig. 3c shows that in addition
to the main peaks of Ba7Nb4MoO20-based oxi
de, there are peaks that belong to Ba4SrNb4O15,
while Ba6Nb3O13.5 or BaMoO4 phases were not
detected. It should be noted that the amount
of Ba4SrNb4O15 phase in BS10NMO powder is
slightly higher compared to that of BS5NMO
powder as indicated by the increased intensity
of the respective peaks.
According to the XRD pattern of BS15NMO
powder in Fig. 3d, an increase in strontium
content to 15 mol.% resulted in the formation
of BaMoO4 and Ba3Nb6O13.5 phases, which have
relatively high intensity of XRD peaks. There
is also a significant increase in the intensity
and number of Ba4SrNb4O15 peaks indicating
an increase in the amount of this phase in the
powder. However, the solid solution of Sr in
Ba7Nb4MoO20 remains as the main phase in the
synthesized powder. The most probable reason
for such a significant increase in the amount
of secondary phases is that Sr reached its solu
bility limit in Ba7Nb4MoO20, and as a result the
excess amount of Sr leads to redistribution of
elements and formation of secondary phases.
It should be noted that the crystal lattice pa-
rameters of (Ba1-xSrx)7Nb4MoO20 phase in
BS10NMO and BS15NMO powders remained
unchanged.
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SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
Fig. 3. XRD patterns of (a) Ba7Nb4MoO20, (b) BS5NMO, (c) BS10NMO, (d) BS15NMO, and (e)
BS20NMO powders. All unmarked peaks correspond to the main (Ba1-хSrх)7Nb4MoO20 phase.
Fig. 3. XRD patterns of (a) Ba7Nb4MoO20, (b) BS5NMO, (c) BS10NMO, (d) BS15NMO, and (e)
BS20NMO powders. All unmarked peaks correspond to the main (Ba1-хSrх)7Nb4MoO20 phase.
According to the XRD pattern shown in Fig. 3a, the powder without the strontium additive
contains two phases, namely Ba7Nb4MoO20 and Ba5Nb4O15, after triple annealing at 1060 oC for 10
h. From the ratio of peaks’ intensity in Fig. 3a, it can be suggested that the amount of Ba5Nb4O15
phase is small.
In the case of BS5NMO powder (Fig. 3b), it can be seen that except the peaks of the main
phase (solid solution of Sr in Ba7Nb4MoO20), there are other peaks which belong to Ba4SrNb4O15
and Ba6Nb3O13.5 phases. The small intensity of the peaks of Ba6Nb3O13.5 indicates that the amount
As can be seen from Fig. 3e, when barium
is partially replaced by 20 mol.% Sr2+, there is a
further remarkable increase in the intensity of
the diffraction peaks of BaMoO4, Ba3Nb6O13.5,
Ba4SrNb4O15, and unidentified phase with a si-
multaneous decrease in the intensity of (Ba1-xS-
rx)7Nb4MoO20 phase, leading to a significant
difference in phase composition from the ex-
pected one. Thus, BS15NMO and BS20NMO
materials cannot be used as an electrolyte for
71https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
H+-SOFCs because they contain a significant
amount of BaMoO4, Ba4SrNb4O15, Ba3Nb6O13.5
phases, which do not possess high ionic or pro-
ton conductivities [30–32].
It should be noted that Sr-based impurity
phases were not detected in the synthesized
powders (Fig. 3). The reason for this lies in
the following facts: (a) Ba and Sr have simi
lar chemical properties; (b) strontium has
smaller ionic radius than that of barium [21];
(c) the used concentration of Sr2+ to dope
Ba7Nb4MoO20 was low (5–20 mol.%). There-
fore, strontium would rather substitute part of
barium atoms in Ba-based compounds than
form separate Sr-based phases.
The crystal lattice parameters of (Ba1-xSrx)7
Nb4MoO20 (x = 0; 0.05, 0.10, 0.15, 0.20) per-
ovskites are given in Table 1. It can be seen that
the crystal lattice parameters of the synthesized
perovskites have a tendency to decrease with
increase Sr content due to the smaller ionic ra-
dius of Sr2+ (1.32 Å) compared to that of Ba2+
(1.49 Å) [21]. The volume of the crystal lattice
of Ba7Nb4MoO20 decreases by ~ 0.57% and ~
0.71% with the addition of 5 mol.% Sr2+ and
10 mol.% Sr2+, respectively. The variations in
the crystal lattice parameters and unit cell vo
lume indicated that the strontium ion is enter-
ing in the lattice of Ba7Nb4MoO20 perovskite.
The crystallite size of (Ba1-xSrx)7Nb4MoO20
(x = 0; 0.05, and 0.10) powders was found to
be in the range of 45–53 nm (Table 1). It fol-
lows the same trend of decreasing values with
increasing strontium content reaching a mini
mum at 10 mol.%. This can be due to the in-
crease in lattice strains because of ionic size
mismatch as ionic size of Sr2+ is lower than
that of Ba2+. The strain increases with the in-
crease in strontium content due to the distor-
tion of the lattice. The incorporation of Sr into
(Ba1-xSrx)7Nb4MoO20 not only produced lattice
distortion but lattice defects and nucleation
centers which inhibits the growth of the pe
rovskite crystals. With increasing the Sr dop-
ing content to 15 mol.% and 20 mol.%, some
fluctuations in the width and intensity of the
two main diffraction peaks of the main phase
are observed (Fig. 3). Although the lattice pa-
rameters remain unchanged (Table 1), the
other structural parameters of BS15NMO and
BS20NMO powders most likely to be affected
by significant amount of impurity phases and
chemical inhomogeneity [25].
Table 1
Structural parameters of (Ba1-хSrх)7Nb4MoO20 perovskites.
Powder
Lattice parameters Unit cell
volume, Å3
Crystallite
size, nm
Lattice
strain, %
Dislocation
density, m-2а, Å b, Å c, Å
Ba7Nb4MoO20 5.861 5.861 16.518 491.4 53 0.264 3.63·1017
BS5NMO 5.852 5.852 16.473 488.6 48 0.299 4.53·1017
BS10NMO 5.842 5.842 16.409 485.1 45 0.308 4.94·1017
BS15NMO 5.842 5.842 16.409 485.1 51 0.267 3.84·1017
BS20NMO 5.842 5.842 16.409 485.1 43 0.317 5.41·1017
72 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
Fig. 4. Particle size distribution of (a) Ba7Nb4MoO20, (b) BS5NMO, and (c) BS10NMO powders.
73https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
Particle size distribution is an important
characteristic of powders that influences their
physical and chemical properties, and, accord-
ingly, their technological properties as well as
the feasibility of their practical use [33]. For
example, the particle size of the powder affects
its behavior during compaction and sintering,
as well as such characteristics of the sintered
products as microstructure, physical and me-
chanical properties [34–38].
In Fig. 4 and Table 2 is presented the re-
sults of the particle size analysis of the powders
with different strontium content in (Ba1-xSrx)7
Nb4MoO20 perovskite. It should be noted that
the particle size distribution and morphology
of BS15NMO and BS20NMO powders was not
studied here due to the significant amount of
the secondary phases that can affect the results.
A comparison of the particle size distribution
of Ba7Nb4MoO20, BS5NMO, and BS10NMO
powders suggests that their size distribution is
approximately the same and does not depend
on the phase and chemical composition of the
powders. The particle size of the synthesized
powders is in the range of 0.05–12 μm, and
their average size is about 2.1 μm.
Table 2
Particle size distribution of (Ba1-хSrх)7Nb4MoO20 powders.
Powder
Size (dn) below which n-percent of the particles is contained, μm
Span
d3 d6 d10 d16 d25 d50 d75 d84 d90 d97
Ba7Nb4MoO20 0.09 0.12 0.50 0.76 1.10 1.90 3.10 3.68 4.28 5.53 1.98
BS5NMO 0.09 0.12 0.49 0.76 1.10 1.90 3.09 3.69 4.27 5.53 1.99
BS10NMO 0.09 0.16 0.69 1.15 1.51 2.54 3.75 4.45 5.16 6.91 1.76
The obtained powders are polydisperse
and show a weak bimodal distribution with
a relatively small fraction of fine particles of
~50–110 nm in size and coarse particles with
sizes from ~0.4 μm to 12 μm. The volume
contribution of the fine fraction does not ex-
ceed 12%. The majority of the particles are
within the 1.5–5 μm size range and the span
of the particle size distribution is 1.76–1.99.
The formation of the coarse powder fraction
is due to the sintering of small particles into
dense aggregates during synthesis at high
temperatures. While the formed aggregates
cannot be effectively destroyed by the applied
methods in this study. The relatively small
particle size of the powders was obtained as
the result of using starting powder materials
with particles less than 5 μm in size, as well as
due to the fast nucleation and slow growth of
(Ba1-xSrx)7Nb4MoO20 phase [39].
Electron microscopic studies were per-
formed to investigate the morphology and
size of (Ba1-xSrx)7Nb4MoO20 particles after so
lid-state synthesis. According to Fig. 5, par-
ticles and their aggregates are characterized
mainly by a rounded irregular shape, which is
the result of formation of new phase, sintering
of nano- and submicron particles, and disin-
tegration of large agglomerates during grind-
ing of synthesis products. Particles and their
74 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
aggregates are characterized by a relatively
wide size distribution, which is in the range of
0.3–10 μm. The size of most particles does not
exceed 5 μm, while the fraction of particles/
aggregates with sizes between about 5 μm and
10 μm is relatively small. According to SEM
analysis of (Ba1-xSrx)7Nb4MoO20 powders, it
can be concluded that the morphology and
particle size of the powder does not depend
on the strontium content. Thus, the effect of
particle size on the powder compaction beha
vior will be the same for powders with different
strontium content [38]. It should be noted that
the results obtained by SEM and laser diffrac-
tion measurements are in good agreement in-
dicating the correctness of the applied research
methods. Our future efforts will be focused on
the preparation of the electrolyte and anode
from the synthesized powders and their cha
racterization for SOFC application.
Fig. 5. SEM images of (a, b) Ba7Nb4MoO20, (c, d) BS5NMO, and (e, f) BS10NMO powders at magnifi-
cation of 2500× (a, c, e) and 10000× (b, d, f).
Fig. 5. SEM images of (a, b) Ba7Nb4MoO20, (c, d) BS5NMO, and (e, f) BS10NMO powders at
magnification of 2500× (a, c, e) and 10000× (b, d, f).
Electron microscopic studies were performed to investigate the morphology and size of
(Ba1-xSrx)7Nb4MoO20 particles after solid-state synthesis. According to Fig. 5, particles and their
aggregates are characterized mainly by a rounded irregular shape, which is the result of formation
of new phase, sintering of nano- and submicron particles, and disintegration of large agglomerates
during grinding of synthesis products. Particles and their aggregates are characterized by a
relatively wide size distribution, which is in the range of 0.3–10 μm. The size of most particles does
not exceed 5 μm, while the fraction of particles/aggregates with sizes between about 5 μm and 10
75https://ucj.org.ua
O. V. Bezdorozhev, I. V. Solodkyi, A. S. Ostroverkh, I. A. Morozov, Y. M. Ostroverkh, Yu. M. Solonin UCJ № 4 / Vol. 88
CONCLUSIONS
The effect of solid-state synthesis conditions
and strontium content on the phase composi-
tion and properties of (Ba1-xSrx)7Nb4MoO20 pow-
ders was studied. It was found that the optimal
temperature interval for solid-state synthesis of
(Ba1-xSrx)7Nb4MoO20 (x = 0; 0.05; 0.10) powders
with a minimum content of secondary phases
is 1060–1080 оС. Moreover, under the applied
synthesis temperatures, the solid-state synthesis
process should be repeated not less than three
times. The X-ray diffraction patterns reveal the
formation of (Ba1-xSrx)7Nb4MoO20 perovskites
with an average crystallite size in the range of
45–53 nm. The crystallite size decreases with
the increase of Sr2+ content due to the increase
in lattice strains which suppress the growth of
the crystals. It was observed that an increase in
the strontium content in (Ba1-xSrx)7Nb4MoO20
above 10 mol.% leads to redistribution of ele
ments and formation of significant amount of
BaMoO4, Ba3Nb6O13.5, and Ba4SrNb4O15. Ac-
cording to the laser diffraction method, the
synthesized (Ba1-xSrx)7Nb4MoO20 powders had
particle size in the range of 0.05–12 μm with
an average size of about 2.1 μm. Moreover, the
size of the particles was found not to depend
on the strontium content and was mainly in-
fluenced by synthesis parameters, size of start-
ing powders, and grinding efficiency after re-
peated annealing operations. These results cor-
relate with the results obtained by electron mi-
croscopy, according to which the particles and
their aggregates have rounded irregular shape.
The study findings indicate that 15 mol.% and
20 mol.% Sr2+-doped Ba7Nb4MoO20 cannot be
used as an electrolyte for H+-SOFCs due to the
significant amount of second phases.
ACKNOWLEDGMENTS. This study
was performed under the project
2020.02/0301 “Development of new
functional materials for the needs of hydro-
gen energy” funded by the National Research
Foundation of Ukraine.
СИНТЕЗ ТА ВЛАСТИВОСТІ ПОРОШКІВ
(Ba1-хSrx)7Nb4MoO20 ДЛЯ ПРОТОН-ПРОВІДНИХ
ТВЕРДООКСИДНИХ ПАЛИВНИХ КОМІРОК
О. В. Бездорожев1,*, Є. В. Солодкий2,
А. С. Островерх1, І. A. Морозов1,
Є. M. Островерх1, Ю. М. Солонін1
1Інститут проблем матеріалознавства
ім. І. М. Францевича НАН України, вул. Кржи
жановського 3, Київ 03142, Україна
2National Національний технічний універ-
ситет України «Київський політехнічний
інститут імені Ігоря Сікорського», просп.
Перемоги 37, Київ 03056, Україна
*е-mail: oleksii.bezdorozhev@gmail.com
Одним із перспективних напрямів ви-
роблення та споживання електричної енер-
гії є воднева енергетика. Для вироблення
електроенергії з водню найефективніше
використовувати електрогенеруючі уста-
новки на основі твердооксидних паливних
комірок (ТОПК) із протонною провідністю
електроліту завдяки їхній високій ефектив-
ності за робочих температур 500–600 оС.
Для використання в ролі електроліту пер-
спективними вважають матеріали на основі
гексагонального перовськіту Ba7Nb4MoO20,
властивості якого можуть бути покраще-
ні шляхом його легування. У зв’язку з цим
76 ISSN 2708-129X. Укр. хім. журн., 2022
SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLSINORGANIC CHEMISTRY
нами було запропоновано здійснити синтез
перовськіту Ba7Nb4MoO20, в якому части-
на атомів барію була б заміщена атомами
стронцію, та відпрацювати умови його син-
тезу. Отже, в цій роботі досліджено вплив
параметрів твердофазного синтезу та вміс-
ту стронцію на фазовий склад та власти-
вості порошків із номінальним складом
(Ba1-хSrx)7Nb4MoO20 (х = 0; 0,05; 0,10; 0,15;
0,20). Для цього використані такі методи
дослідження, як рентгенівська дифракція,
скануюча електронна мікроскопія та ла-
зерна дифракція. Відповідно до результа-
тів рентгенофазового аналізу порошків,
синтезованих за 1000–1100 оС, встанов-
лено, що оптимальним температурним
інтервалом для одержання перовськітів
(Ba1-хSrх)7Nb4MoO20 (х = 0; 0,05; 0,10) із мі-
німальним вмістом вторинних фаз є 1060–
1080 оС. Тоді як необхідна кількість повтор-
них відпалів по 10 год має бути не менше
трьох. При вмісті стронцію 15 мол.% та
20 мол.% спостерігаємо суттєве зростання
вмісту вторинних фаз (BaMoO4, Ba4SrNb4O15,
Ba6Nb3O13,5) внаслідок досягнення границі
розчинності Sr в Ba7Nb4MoO20, що виключає
можливість використання зазначених пе-
ровськітів як електроліту ТОПК. Досліджен-
ня гранулометричного складу порошків
(Ba1-хSrх)7Nb4MoO20 (х = 0; 0,05; 0,10) показа-
ло, що дисперсність порошків не залежить
від їхнього хімічного складу та визнача-
ється в основному дисперсністю вихідних
речовин, умовами синтезу та ефективніс-
тю подрібнення порошку після повторних
операцій відпалу. Встановлено, що розмір
частинок порошків (Ba1-хSrх)7Nb4MoO20 зна-
ходиться в діапазоні 0,05–12 мкм, тоді як
їхній середній розмір складає 2,1 мкм. Ці
результати співпадають із результатами
електронної мікроскопії, відповідно до якої
частинки порошку мають неправильну
округлу форму, яка зумовлена процесами
формоутворення, що відбуваються під час
утворення нової фази з вихідних речовин,
руйнування/агломерації частинок під час
подрібнення продуктів синтезу та спікання
малих частинок під дією температури.
Ключові слова: твердофазний синтез,
перовськіт, порошок, Ba7Nb4MoO20, елек-
троліт.
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Стаття надійшла 16.04.2022.
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| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-433 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:08:05Z |
| publishDate | 2022 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/5d/73ca49d9bf8a8fb97ece27ae87d9d75d.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-4332026-07-22T08:23:49Z SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS Bezdorozhev, Oleksii Solodkyi, Ievgen Ostroverkh, Anna Morozov, Igor Ostroverkh, Yevhenii Solonin, Yuriy solid-state synthesis, perovskite, Ba7Nb4MoO20, powder, electrolyte. This work reports on the preparation and characterization of Sr2+-doped Ba7Nb4MoO20 powders prepared by a solid-state synthesis as promising materials for solid oxide fuel cells. The influence of synthesis parameters and strontium content (x = 0; 0.05; 0.10; 0.15; 0.20) on the phase composition and properties of (Ba1-xSrx)7Nb4MoO20 powders was studied. The results of the phase analysis show that (Ba1-xSrx)7Nb4MoO20 (x = 0; 0.05; 0.10) powders with a minimum amount of secondary phases can be obtained after at least three repeated synthesis cycles at 1060–1080 оС for 10 h. According to the laser diffraction analysis, the synthesized powders comprise particles with a polydisperse size distribution spreading from 0.05 μm to 12 μm and average particle size of 2.1 μm. Electron microscopy observations support these findings and demonstrate that the particles and their aggregates have rounded irregular shape. Moreover, it was found that the morphology and particle size of the powder does not depend on the strontium content. Doping (Ba1-xSrx)7Nb4MoO20 with 15 mol.% and 20 mol.% Sr2+ leads to the formation of a significant amount of secondary phases due to exceeding the solubility limit of strontium, thus making these compositions unsuitable for use in solid oxide fuel cells. V.I.Vernadsky Institute of General and Inorganic Chemistry 2022-05-25 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/433 10.33609/2708-129X.88.04.2022.63-78 Ukrainian Chemistry Journal; Vol. 88 No. 4 (2022): Ukrainian Chemistry Journal; 63-78 Украинский химический журнал; ##issue.vol## 88 ##issue.no## 4 (2022): Ukrainian Chemistry Journal; 63-78 Український хімічний журнал; Том 88 № 4 (2022): Український хімічний журнал; 63-78 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/433/221 Copyright (c) 2022 Oleksii Bezdorozhev, Ievgen Solodkyi, Anna Ostroverkh, Igor Morozov, Yevhenii Ostroverkh, Yuriy Solonin https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Bezdorozhev, Oleksii Solodkyi, Ievgen Ostroverkh, Anna Morozov, Igor Ostroverkh, Yevhenii Solonin, Yuriy SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title | SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title_full | SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title_fullStr | SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title_full_unstemmed | SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title_short | SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS |
| title_sort | synthesis and characterization of (ba1-хsrx)7nb4moo20 powders for proton-conducting solid oxide fuel cells |
| topic_facet | solid-state synthesis perovskite Ba7Nb4MoO20 powder electrolyte. |
| url | https://ucj.org.ua/index.php/journal/article/view/433 |
| work_keys_str_mv | AT bezdorozhevoleksii synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells AT solodkyiievgen synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells AT ostroverkhanna synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells AT morozovigor synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells AT ostroverkhyevhenii synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells AT soloninyuriy synthesisandcharacterizationofba1hsrx7nb4moo20powdersforprotonconductingsolidoxidefuelcells |