New Journal of Glass and Ceramics, 2011, 1, 58-62
doi:10.4236/njgc.2011 .12007 Published Online July 2011 (http://www.SciRP.org/journal/njgc)
Synthesis and Characterization of
La0.75Sr0.25Cr0.5Mn0.5O3-δ Nanoparticles
Using a Combustion Method f or Solid Oxide
Fuel Cells
V. S. Reddy Channu1, Ru d ol f Ho lz e1, E dwin H. Walker Jr.2, Rajamohan R. Kalluru3
1Institut für Chemie, AG Elektrochemie, Technische Universität Chemnitz, Chemnitz, German y; 2Department of Chemistry, South-
ern University and A&M College, Baton Rouge, USA; 3KITE College of Professional Engineering Sciences, Jawaharlal Nehru
Technological University of Hyderabad, Shabad, India.
Received April 11th, 2011; revised May 9th, 2011; accepted May 16th, 2011.
ABSTRACT
La0.75Sr0.25Cr0.5Mn 0. 5O3-δ (LSCM) perovskite nanoparticles for use as anode material in intermediate temperature solid
oxide fu el cells (IT-SOFCs) w e re syn th esi zed usi ng 3,3’,3”-nitrilotripropio nic a cid (NTP), citric acid and oxalic acid as
carriers via a combustion method. The influence of the carrier on phase and morphology of the obtained pristine prod-
ucts was characterized using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and scanning electron mi-
croscopy (SEM). XRD results showed, that the LSCM had rhombohedral symmetry with R-3c space group; a single
phase LSCM perovskite formed after calcination of fired gel at 1200˚C for 7 h. Scanning electron microscopy analysis
of the pristine powders showed spherical shape and particle sizes in the range of 50 - 500 nm..
Keywords: Nanoparticles, Combustion method, Morphology, Carriers
1. Introduction
A fuel cell is an electrochemical device that converts
chemical energy of fuels (hydrogen, methane, butane or
even gasoline and diesel) into electrical energy by ex-
ploiting the natural tendency of oxygen and hydrogen to
react. Fuel cells are simple devices co nta ini ng no mo vin g
parts and only four functional components namely ca-
thode, electrolyte, anode and interconnect. Solid oxide
fuel cells (SOFCs) are considered to be among the most
versatile power production facilities. Their unique cha-
racteristics include extre me efficiency, sig nificant energy
conversion rate with a wide range of fuels and pollu-
tion-free operation. On the other hand high operating
temperature (about 1000˚C) of the SOFC results in pro b-
lems including difficult sealing between cells with flat
plate configurations and thermal expansion mismatches
between components. In addition, the high operating
temperature places rigorous constraints on materials se-
lection and results in difficult fab rication proc e sses [1].
Recently, perovskite based conducting oxides, such as
substituted lanthanum chromites or lanthanum manga-
nates and strontium titanates, received great attention as
alternative anode materials for solid oxide fuel cells [2].
Particularly, (La0.75 Sr 0.25)1-xCr0.5 Mn 0.5O3−δ perovskite phase
(LS C M) has been considered as a capable anode material
for SOFCs d ue to its electro catal ytic/catalytic acti vity for
oxidation of methane fuel in the absence of steam, re-
duced carbon deposition, and high durability a gainst sul-
fur poisoning and good electrical properties [3,4]. Pre-
dominantly, this composition of LSCM has shown good
stability in fuels and in air, and has good resistance to-
wards carbon deposition and low polarization resistance
when used with hydrocarbon fuels [5]. LSCM can also
be used as a cathode, thus facilitating fuel cells with a
symmetrical structure (LSCM/electrolyte/LSCM) [6,7].
Up till now, various chemical methods were reported
in the literature for the synthesis of LSCM powders, for
example, glycine nitrate method [3], EDTA (ethylenedia
minetetraacetic acid) chelating method [8,9], combustion
synthesis [7,10], solid-state reactio n [4,6,11-15], gel-casting
[16,17] and co-prec ipitation method [18 ]. The so lid-state

Synthesis and Characterization of La0.75Sr0.25Cr0.5Mn0.5O3-δ Nanoparticles
Using a combustion M ethod for Solid Oxide Fuel Cells
59
method has some disadvantag es suc h as high temperature
(above 1300˚C) and long duration of synthesis of LSCM
and non-homogeneity in pa rticle size and low purity [19].
However, to synthesize homogeneous fine particles of
pure phase LSCM powders requires low temperature and
short duration of synthesis. The solution combustion
method is suitable to synthesize nanosize LSCM particles
with good homogeneity [20]. The present work reports on
the synthesis of nanostructured La0.75Sr 0. 25 Cr0.5Mn0.5 O3−δ
(LSCM) perovskite by a combustion method using
3,3’,3”-nitrilotripr opionic ac id, oxalic acid and citric acid
as carriers.
2. Experimental
Nanostructured La0.75Sr0. 25Cr0.5Mn0.5O3−δ (LSCM) pero-
vskite anode material was synthesized by a combustion
technique. Three batches of LSCM solutions are pre-
pared with stoichiometric amounts of lanthanum nitrate
(La(NO3)3·6H2O), strontium nitrate (Sr(NO3)2), chro-
mium nitrate (Cr(NO3)3·9H2O) and manganese nitrate
(Mn(NO3)2) in distilled water under constant stirring.
First, a stoichiometric amount of citric acid (C6H8O7
H2O) and 15 ml ethyle ne glycol, second, oxalic acid and
15 ml ethylene glycol, and 3,3’,3”-nitrilotripro pionic acid
and 15 ml et h yle ne gl yc ol whi c h ar e che latin g a ge nt s a nd
fuel, were also dissolved in LSCM solution. The stoi-
chiometric ratio of carriers to nitrates was 2 [21]. A gel
was formed with continuous stirring and mild heating at
120˚C. The gel was dried at room temperature for over-
night a nd the n heated at 350˚C for 30 min. The resulting
powders were ground in an agate mortar and heated in air
at 1000˚C for 7 h. F inal l y, the ground product was heated
at 1200˚C for 7 h in air.
Crystallographic information of the samples was ob-
tained using an X-ray powder diffractometer (D8 Ad-
vanced Brucker) with graphite monochromatized Cu Kα
radiation (λ = 1.54187 Å). Diffraction data were col-
lected over the 2θ range of 15˚ to 80˚. The morphologies
of the resulting products were characterized using a
scanning electron microscope (SEM, JEOL JSM 6390).
For the TGA measurements a TA 600, operating in dy-
namic mode (heating rate = 10˚C/min) , was employed.
3. Results and Discussion
Phase purity and crystallographic information of the
synthesized La0.75Sr0.25Cr0.5Mn0.5O3-δperovskite nanopar-
ticles were characterized using powder X-ray dif fraction.
The XRD patterns of LSCM perovskite nanoparticles
are shown in Figure 1. All diffraction patterns of
La0.75Sr0. 25Cr0.5Mn0.5O3-δ perovskite nanoparticles show
characteristic peaks of the perovskite phase. The XRD
patterns are in good agreement with the standard data for
rhombohedral symmetry with a = 5.4736 Å, b = 5.4736
Å, c = 13.2898 Å and R-3c space group (JCPDS #
01-070-8673). No impurity phases were observed pre-
sumably because in the solid-state reaction the pure
phase of La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM ) perovskite
was formed at 1200˚C [21]. The crystallite size of the
LSCM nanoparticles was calculated using Debye-Scherrer
formula at (110) plane. The size of the LSCM-particles
prepared NTP-assisted is 57.65 nm, with citric acid and
oxalic acid the value is 68.63 nm.
In the synthesis of La0.75Sr 0. 25Cr0.5Mn0.5O3-δ (LSCM)
perovskite nanoparticles the carriers (NTP, oxalic acid
and c itri c aci d) he lp i n ob tai ning a ho moge neous mi xtur e
of the cations in a solution through forming metal com-
plexes, they also help in the reduction of nitrates in a
combustion process, releasing a large amount of heat.
This is sho wn by an exothermic peak at 377˚C on a DS C
curve (Figure 2). During the solid-state reduction
process, metal cations and oxygen anions stay in the
react and mixture during the formation of perovskite
phase in t his combustion process. The large heat released
during combustion might be of the help to overcome the
lattice energy, which is required for the formation of the
perovskite phase, and also the completion of the nu-
cleation by the rearrangement of atoms by short distance
diffusion. The fast combustion process might not be of
help for the diffusion of atoms far from each other and
hence the particle size of LSCM powder remained in the
nanometer range [22].
Thermogravimetric analysis and differential scanning
calorimetry (TGA-DSC) curves with NTP-assisted
LSCM dried as a gel at 120˚C are sho wn in Figure 2. The
weight losses happen in three steps. The total weight loss
20 30 40 50 60 7080
La
0.75
Sr
0.25
Cr
0.5
Mn
0.5
O
3-δ
(NTP +EG at 1200
O
C)
2θ/°
57.65 nm
68.63 nm
La
0.75
Sr
0.25
Cr
0.5
Mn
0.5
O
3-δ
(OA+EG at 1200
O
C)
68.63 nm
La
0.75
Sr
0.25
Cr
0.5
Mn
0.5
O
3-δ
(CA+EG at 1200
O
C)
Intensity/s
-1
(214)
(024)
(006)
(202)
(113)
(104)
(110)
(JCPDS # 01-070-8673)
(012)
Figure 1. XRD patterns of La0.75Sr0.25Cr0.5Mn0.5O3-δ
(LSCM) perovskite phase nanopa rt icles.

Synthesis and Characterization of La0.75Sr0.25Cr0.5Mn0.5O3-δ Nanopar ticles
Using a Combustion Method for Solid Oxide Fuel Cells
60
0200 400 600 800100012001400
3
4
5
6
LaSrCrMnO
3
+NTP
0.5mg
0.33mg
TGA
DSC
Temperatur e/
O
C
W eight loss/mg
1.25 mg
-300
-200
-100
0
100
200
Heat flow (mW )
Figure 2. TGA-DSC curves of La0.75Sr0.25Cr0.5Mn0.5O3-δ
(LSCM) perovskite g el precursor dried at 120˚C.
was 2.1 mg from room temperature to 1300˚C. The first
weight loss is 0.33 mg in the temperature range 22˚C -
236˚C; this can be attributed to evaporation of water
from the layers of LSCM. The second weight loss is 1.25
mg in the tempera ture ra nge 236˚C - 383˚C and the third
weight loss is 0.5 mg in the temperature range 383˚C -
837˚C. The second and third weight losses are attributed
to decomposition of the carrier (NTP) and evaporation of
structurally bounded water. The peaks located at about
295˚C and 377˚C are exothermic on the DSC curve due
to decomposition of nitrates and organic matter and cor-
respond to the second weight loss of 1.25 mg from about
236˚C to 400˚C as observed in the TGA curve.
To observe thermal effects above 350˚C, different
carrier-assisted LSCM samples were fired at 350˚C for 1
h. F igure 3 shows T GA-DT A cur ves of t he di ffere nt c ar-
rier’s assisted LSCM samples. The total weight loss was
0.97 mg in NTP assisted LSCM, 0.39 mg in oxalic acid
assisted LSCM, and 0.77 mg in citric acid assisted
LSCM from room temperature to 1300˚C. The first
weight loss is 0.32 mg in NTP assisted LSCM in the
temperature range 30˚C - 490˚C, whereas the first weight
loss is 0.2 mg in the oxalic acid used LSCM in range
30˚C - 338˚C and the first wei ght loss is 0.2 5 mg in citric
acid used LSCM in range 30˚C - 334˚C. The second
weight loss is 0. 9 mg in NT P used LS CM in the t emper-
ature range 490˚C - 822˚C, whereas the second weight
loss is 0.42 mg in citric ac id used LSCM in range 334˚C -
688˚C. The second weight loss was attributed to the reac-
tion between the residual nitrate and carriers after the
decomposition of the precursor and subsequent combus-
tion of organic components.
The morphologies of La0.75 Sr0.2 5 Cr0.5Mn0. 5O3 -δ pe-
rovskite nan-oparticles synthesized using different car-
02004006008001000 1200 1400
3.5
4.0
4.5
5.0
5.5
6.0
0.42mg
0.25mg
0.2mg 0.9mg
LaSrCrMnO
3
+NTP
LaSrCrMnO
3
+ C it iric Ac id
LaSrCrMnO
3
+ Ox a lic Acid
W eight loss/mg
Temperature/
O
C
0.32mg
Figure 3. TGA curves of La0.75 Sr0.25Cr0. 5Mn0.5O3-δ (LSCM)
perovskite gel precursor dried at 120ºC and then fired at
350˚C for 1h.
(a)
(b)
(c)
Figure 4. SEM images of La0.75Sr0.25Cr0.5Mn0.5O3-δ perovs-
kite phase nanoparticles (a) NTP-assisted, (b) oxalic acid
assisted and (c) citric acid assisted.
1μm
1μm
1μm

Synthesis and Characterization of La0.75Sr0.25Cr0.5Mn0.5O3-δ Nanoparticles
Using a combustion M ethod for Solid Oxide Fuel Cells
61
riers by combustion method as examined with scanning
electron microscopy are show n in Fig ure 4. NTP-assisted
LSCM shows many nanosized particles of sphe ricalshape
in the range 100 - 500 nm (Figure 4(a)). The LSCM
powders synthesized using oxalic acid and citric acid as
carriers consist of uniform nanoparticles shwoing less
agglomeration. The average particle size of the
La0.75Sr0. 25Cr0.5Mn0.5O3-δ perovskite powders calcinated
at 1200˚C is about 50 - 500 nm (Figures 4(a) and (b)).
The small size La0.75Sr0.25Cr0.5Mn0.5O3-δ perovskite nano-
particles are very active, small size is also beneficial for
decreasing the fabrication temperature of the anode film
and enhancing the catalytic proper ties.
4. Conclusions
La0.75Sr0. 25Cr0.5Mn0.5O3-δ (LSCM) perovskite phase na-
noparticles were successfully synthesized by solution
combustion method using different carriers (NTP, oxalic
acid, and citric acid) after calcination of fired gel at
1200˚C for 7 h. Scanning electron microscopy of the
as-synthesized powders showed spherical particle shapes
and sizes in the range of 50 - 500 nm. An exothermic
reaction between carriers and nitrates initiates the com-
bustion process. TGA and DSC analysis confirmed the
decomposition process of nitrates and the organic matter.
The combustion reactions took place in the temperature
range 200 ˚C to 400˚C.
5. Acknowledgements
One of the authors (V S Reddy Channu) thanks the Al-
exander von Humboldt Foundation for a fellowship.
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