PO 27

1. Introduction
機械 機械手臂大氣電漿噴塗
機械 臂大氣電漿噴塗 LSGM 電解質層性質研究
電解質層性質研究
Properties of LSGM Electrolyte Produced by Robotic
Atmospheric Plasma Spraying
羅志宏 黃振興 蔡俊煌
Chih-Hung Lo, Chang-Sing Hwang, Chun-Huang Tsai
核能研究所物理組
Physics Division, Institute of Nuclear Energy Research
Abstract
LSGM electrolyte was found to be an electrolyte for the intermediate
temperature (500-800℃) solid oxide fuel cells (SOFCs). In this paper, dense
LSGM electrolyte layers with a thickness around 100μm for SOFC were
produced using robotic atmospheric plasma spraying, followed by post
heat-treatment at elevated temperatures of 600-900 ℃ . The as-sprayed
electrolyte exhibits a single LSGM phase in a mixture of amorphous and
crystalline states. Fortunately, the amorphous phase can be completely
transferred into a crystalline phase at post heat-treatment temperature above
700℃. The physical and electrochemical properties of gas-tight LSGM
electrolyte have been characterized by FESEM, XRD, EDX and
electrochemical impedance spectroscopy (EIS) measurements and analysis,
including phase purity, crystallization, density, open circuit voltage (OCV)
and ionic conductivity.
Keywords: LSGM, Solid Oxide Fuel Cells (SOFCs), Atmospheric Plasma
Spraying (APS)
Solid oxide fuel cells is capable of
generating electric power through the chemical
reaction between gaseous fuel such as hydrogen
and oxygen with high efficiency, and further
their mechanical reliability can be improved and
fabricating cost can be reduced by reducing cell
operating temperature. Therefore, the
development of intermediate temperature solid
oxide fuel cell (IT-SOFC) is an important step
towards SOFC commercialization.
In the past years, several approaches have
been made to the fabrication and
characterization of LSGM for SOFC. The
convention ceramic processes like slurry coating
[1] and tape casting [2], chemical vapor
deposition (CVD) techniques such as
electrostatic assisted vapor deposition (EAVD)
[3] and atomic layer epitaxy (ALE) [4], physical
deposition processes such as pulsed laser
ablation (PLA) [5, 6], electrophoretic deposition
(EPD) [7] and atmospheric plasma spraying
(APS) [8]. Thermal spray techniques, vacuum
plasma spraying was considered highly

promising for producing thin and dense
electrolyte layer such as yttria stabilized
zirconia (YSZ) in most case. The study use
inexpensive and universal APS system for
integrated fabrication of dense electrolyte for a
medium temperature button cell. Therefore, the
technical issues associated with high density
electrolyte deposition by APS, it is quite
possible for fabricating high density electrolyte
layer by APS if new electrolyte material is
selected. For this reason, strontium- and
magnesium-doped LaGaO3 perovskite oxide
(LSGM) has been proposed as a possible
electrolyte material for IT-SOFCs [9-12].
The aim of this present paper is to
evaluate the potential of the robotic atmospheric
plasma spraying technique in producing thick
films of LSGM. As well as to test and evaluate
the physical and electrochemical properties of
the button cell at temperatures for IT-SOFCs.
2. Experimental apparatus
The robotic APS system consists of
mainly a DC plasma spray gun (Model SG-100,
Praxair) that generates a high temperature
plasma flame under atmospheric condition, a
robotic (FANUC Robot ARC Mate 120iB) that
holding plasma spray gun to scan substrate, a
powder feeder for delivering plasma sprayable
powders, a cooling system for the torch, a heater
for preheating the substrate, an IR detector for
measuring the temperature of the substrate and a
fast CCD camera to observe trajectories of
particles in the plasma flame. Figure 1
schematically depicts the experimental set-up.
The plasma sprayable La0.8Sr0.2Ga0.8
Mg0.2O3 powders (LSGM, Inframat Inc.) are
injected radially into the copper anode nozzle at
the position 1.4 cm inward away from the
nozzle's exit. These powders have an average
size of 40-60 μm. These powders enter the
plasma flame generated by a DC plasma torch,
which heated and accelerated by the plasma
flame to produce LSGM coatings on φ 24mm
porous YSZ/Ni cermets anode. The operation
parameters of atmospheric plasma spraying for
LSGM are presented in Table 1.
Figure 1 Schematic drawing of robotic
atmospheric plasma spray system.
Table 1 Atmospheric plasma spraying process
parameter for deposition of LSGM.
Parameter Value
Power 28-40 kW
Current 370-450 A
High purity Argon gas flow rate 45-68 slpm
Helium 15-38 slpm
Hydrogen gas flow rate 3-12 slpm
Powder feed rate 2-15 g/min
Powder carry gas flow rate 2-8 slpm(Argon)
Spray distance 6-10 cm
Preheated substrate temperature
450-850 ℃
Shroud gas flow rate 35-60 slpm
Robot scan speed 100-1000 mm/sec
YSZ/Ni cermet and φ 24mm
porous Ni
substrates with a thickness of 2 mm. Substrates

are scanned by a robot to coat an area ofφ 24mm
.
The speed of the robot can be adjusted to as
high as 2000 mm/sec. All coating experiments
were conducted in the soundproof cabinet
shown in Figure 1 to reduce the sound noise
generated by the plasma torch. Table 1 presents
typical operating parameters. FESEM, TEM,
XRD, EDX and electrochemical impedance
spectroscopy (EIS) equipment is adopted to
analyze the coatings prepared in this study.
3. Results and Discussion
The LSGM electrolyte layer was plasma
sprayed onto the YSZ/Ni anode layer. A novel
YSZ/Ni anode coating with nanostructured
features was produced [13].
The X-ray diffraction patterns are shown
in Figure 2, XRD analysis was handled for
starting LSGM feedstock and as-spray
deposition. The LSGM powder was identified
by a single phase, nevertheless, the as-sprayed
LSGM layer by amorphous phase characterized
from the standard peaks. In order to investigate
the transition temperature for the crystallization
of the sprayed LSGM deposition, the deposition
was exposed to post heat-treatment at various
temperature from 600 to 900 ℃. XRD data
indicate that LSGM deposition becomes to show
low degree of crystallization after the heat
treatment temperature exceeds 600 ℃, and a
high degree of crystallization is identified above
700 ℃ was shown in Figure 3,. From the point
of oxygen ion conductivity, the formation of the
amorphous phase in the LGSM layer is
definitely negative. Fortunately, the XRD data
confirmed that the chemical stoichiometry for
the deposit is not altered, such as there is no
decomposition occurring in the spray process,
and full crystallization can be achieved in a post
heat treatment at medium temperature.
Lin (conuts)
200
150
100
50
0
300
200
100
0
20 30 40 50 60 70 80
2-Theta (degree)
LSGM APS layer
LSGM feedstock
Figure 2 X-ray diffraction patterns for LSGM
feedstock powder and as-sprayed deposition
Lin (counts)
200
100
0
200
100
0
200
100
0
100
0
100
0
Heat treatment at 900 oC, 1hr
Heat treatment at 800 oC, 1hr
Heat treatment at 700 oC, 1hr
Heat treatment at 600 oC, 1hr
LSGM APS layer
without heat treatment
20 30 40 50 60 70 80
2-Theta (degree)
Figure 3 X-ray diffraction patterns of the
sprayed LSGM deposition after heat treatment
in the air atmosphere at different temperature.
Figure 4 was shows the FESEM image of
the sprayed LSGM deposition cross section
view. Generally viewing, the LSGM deposition
layer is formed with a high density, uniform
thickness and satisfactory interfacial connection
with the porous YSZ-NiO anode. The main
defect is isolated pores, probably attributing to

the inclusion of some un-melted large-size
particles. Normally, the LSGM deposition layer
is 100μm thick.
Figure 4 FESEM cross section view of the
sprayed LSGM deposition.
Figure 5 shows Arrhenius plots of
oxide-ion conductivity for the as-sprayed LSGM
deposition layer at the measured temperature
range of 600-800 ℃ . While the measured
temperature at 600, 700 and 800 ℃ , the
conductivity of the LSGM deposition layer is
3.60 × 10 -3 , 4.69 × 10 -3 and 7.09 × 10 -3 Scm -1
respectively. Furthermore, the activation energy
was calculated to be 0.65 eV. It is dissimilar to
the value of 0.998 eV with the report by Li et al.
[14]. From the present, the density of the
electrolyte and its phase’s impurity should be
the main factors influencing on the activation
energy of LSGM.
The LSGM electrolyte layer has been
deposit by atmospheric plasma spraying and its
microstructure is shown in Figure 4. The
electrolyte layer electrical performance was
evaluated by open circuit voltage (OCV) at
temperature 500-800℃. The result of OCV,
0.96V at 760℃ and 0.982V at 700℃ is shown
in Figure 6. Thus it can be seen, the OCV
measured data has satisfactory gas tightness that
atmospheric plasma spraying deposit LSGM
electrolyte layer.
log σ Τ (S cm -1 K)
0.9
0.8
0.7
0.6
0.5
0.4
0.9 0.95 1 1.05 1.1 1.15
T -1 10 3 (K -1 )
Figure 5 Arrhenius plots of the LSGM
electrolyte layer prepared by APS.
E (Volts)
1.2
1.0
0.8
0.6
0.4
0.2
0
0 250 500 750 1000 1250 1500 1750 2000
Time (Sec)
Figure 6 Open circuit voltage of the LSGM
electrolyte layer measured from 760 to 700℃.
4. Conclusions
760℃ 700℃
The results presented in this study
demonstrate that gas tight LSGM electrolyte
layer can be successfully formed by the robotic
APS system. The as-sprayed LSGM electrolyte
layer contained an amorphous phase; however,
crystallization LSGM could be achieved by heat
treatment at temperature above 700 ℃ .
Electrochemical impedance spectra indicated
that the fully crystallized LSGM electrolyte has
a high conductivity. With a good gas tightness

of the dense LSGM electrolyte, a half-cell open
circuit voltage close to theoretical value was
measured, which will operate at a medium
temperature 500-800℃.
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