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S. Paengson et al./Journal of Materials Science and Applied Energy 4(1) (2015) 9-12
9
P-Ca3Co4O9 DOPED Ag AND N-Ca0.97Bi0.03MnO3 MATERIALS
FOR THERMOELECTRIC REFRIGERATOR
Supasit Paengson1, Kunchit Singsoog
1,2, Panida Pilasuta
1,
Wanatchaporn Namhongsa1, and Tosawat Seetawan
1,2*
1Program of Physics, Faculty of Science and Technology, Sakon Nakhon Rajabhat University,
Sakon Nakhon, 47000, Thailand 2Thermoelectrics Research Center, Research and Development Institution, Sakon Nakhon
Rajabhat University, Sakon Nakhon, 47000, Thailand
Received 22 December 2014; Revised 15 April 2015; Accepted 15 April 2015
ABSTRACT
Generally, the thermoelectric refrigerator fabricated form semimetal such as Bi2Te3, PbTe, and
SiGe which high performance materials but a semimetal has toxic, expensive, and sensitive electrical
shock. In this work, the possibility using oxide materials for fabricated thermoelectric refrigerator.
The oxide thermoelectric refrigerator was fabricated from P-Ca3Co4O9 doped Ag and N-Ca0.97Bi0.03MnO3 materials. These materials were synthesized by solid state reaction method. The
fabrication using melting method for connected materials with aluminum electrode. The thermoelectric
properties were measured by steady state method for evaluated dimensionless figure of merit (ZT) and
coefficient of performance (COP).
KEYWORDS: oxide thermoelectric refrigerator, P-Ca3Co4O9 doped Ag, N-Ca0.97Bi0.03MnO3, coefficient of
performance
* Corresponding authors; e-mail: t_seetawan@snru.ac.th, Tel.&Fax +6642744319
INTRODUCTION
The thermoelectric refrigerator or thermoelectric
cooler are used Peltier effect for change electrical
power to temperature gradient [1]. Normally thermoelectric materials for fabrication
thermoelectric refrigerator used semimetal such as
Bi2Te3, PbTe, and SiGe (ZT ≈ 0.3-0.17) [2, 3]
which high performance and good thermoelectric
properties. The performance of thermoelectric
materials is determined by dimensionless figure of
merit (ZT) [1].
2S T
ZT
(1)
where S , , and T is Seebeck coefficient,
electrical resistivity, thermal conductivity and
absolute temperature respectively. The coefficient
of performance (COP) for refrigerator has directly
related to ZT value [1,4].
m
max
m
( 1 )
( 1 1)
h
c c
h c
TZT
T TCOP
T T ZT
(2)
where cT and
hT are cold side and hot side
temperature of thermoelectric materials
respectively, and mZT is figure-of-merit at
average temperature of cT and
cT . The fabrications
of thermoelectric refrigerator are connecting
materials series, but are thermal parallel. Major development of oxide thermoelectric
materials concentrated to fabrication generator
but using oxide materials for refrigerator so few.
The aims of this research are measured
thermoelectric properties, dimensionless figure of
merit and coefficient of performance oxide
refrigerator fabricated from P-Ca3Co4O9 doped
Ag and N-Ca0.97Bi0.03MnO3
MATERIALS AND METHODS
1) Synthesis and Fabrication
The P-Ca3Co4O9 doped Ag and N-
Ca0.97Bi0.03MnO3 bulks prepared form powder
P-Ca3Co4O9 doped Ag and N- Ca0.97Bi0.03MnO3
which synthesized by solid state reaction method
or SSR method. Firstly we using calcium
carbonate powder (CaCO3 100.09 g/mol, purity 99%, Sigma-Aldrich Co.) were mixed with cobalt
S. Paengson et al./Journal of Materials Science and Applied Energy 4(1) (2015) 9-12
10
oxide powder (Co2O3 165.86 g/mol, purity 99.9%, Sigma-Aldrich Co.) and silver (Ag 87
g/mol, purity 99.9%). The N-type used calcium
carbonate powder mixed with manganese dioxide
(MnO2 86.94 g/mol, purity 99.9%, Ajax Finechem Pty Ltd.) and bismuth oxide (Bi2O3
465.96 g/mol purity 99.9%, Sigma-Aldrich Co)
purity in molar ratios. The mixed CaCO3+Co2O3+Ag
for P-Ca3Co4O9 doped Ag and mixed CaCO3+
MnO2+Bi2O3 for N-Ca0.97Bi0.03MnO3 were calcined
at 1123 K for 10 h and 1323 K for 24 h in air,
respectively. The calcined P-type powder was
pressured of 21.57 MPa due to bulks sintered at 1223
K for 12 h. The calcined N-type powder was
pressured of 9.80 MPa for bulks sintered at 1423
K for 36 h in air, respectively. Subsequently, the sintered bulks were cutting and polishing using
the precision saw and grinder polisher (Isomet
Low Speed Saw and WaterServ 3000 Ltd, USA)
to obtain the legs shape of the thermoelectric cell.
Confirm powder by x-ray diffraction (XRD)
patterns have been performed on XRD-6100
SHIMADZU real time multiple strip detector,
using Cu-Kα radiation and operating at 2 kW
room temperature. The scans have been recorded
from 10º to 80º (2). Thermoelectric properties Seebeck coefficient, electrical resistivity and
thermal conductivity of the bulks sintered
measurement by steady state ranging around 303K to 473K. Thermoelectric refrigerator cell
was fabricated from P-N legs size of 2.5×2.5×10
mm3 prior connect P-N junction must solder Pb
on top and bottom legs for could connect with
aluminum electrode. The total resistant of
thermoelectric refrigerator cell is ≈ 2.5 Ω. How to
select P and N legs for fabricated thermoelectric
refrigerator cell are selected from synthesis
condition has lowest total resistant of P-Ca3Co4O9
doped Ag and N-Ca0.97Bi0.03MnO3 bulks.
2) Measurement coefficient of performance
Fig. 1. modeling measurement of thermoelectric
refrigerator cell
Fig.1 shown modeling measurement system of thermoelectric refrigerator cell. The red wire
from refrigerator cell connected with the positive
power supply and the black wire connected with
negative power supply measured compared heat
adsorbed (cold side) and heat rejected hot side
temperature by thermocouple K-type. [5]
RESULTS AND DISCUSSION
Thermoelectric properties
280 320 360 400 440 480
120
160
200
240
120
160
200
2403 2(175.29 0.77 1.91 10 ) 34.67S T T
P-Ca3Co
4O
9 doped Ag
Seebeck C
oeff
icie
nt (
V/K
)
Temperature (K)
(a)
280 320 360 400 440 480
-400
-360
-320
-280
-240
-200
-400
-360
-320
-280
-240
-200
(b)
-217.38-0.077exp(0.02137 ) 0.70S T
N-Ca0.97
Bi0.03
MnO3
Seebeck C
oeff
icie
nt (
V/K
)
Temperature (K)
Fig. 2. Temperature dependence of the Seebeck
coefficient for bulks P-Ca3Co4O9 doped Ag and
N-Ca0.97Bi0.03MnO3
The relationship of Seebeck coefficient and
temperature of P-Ca3Co4O9 doped Ag at 303-473
K as shown Fig.2 (a). The Seebeck coefficient of
P-Ca3Co4O9 doped Ag values were linearly
increased with increasing temperature. The relationship of Seebeck coefficient and temperature
of Ca0.97Bi0.03MnO3 at 303-473 K as shown Fig.2
(b). The Seebeck coefficient of Ca0.97Bi0.03MnO3
values were exponentially increased with
increasing temperature.
280 320 360 400 440 480
0.35
0.40
0.45
0.35
0.40
0.45
5 2(-1.28 0.009 -1.12 10 ) 0.07T T
P-Ca3Co
4O
9 doped Ag
Ele
ctr
ical R
esis
tivity (
mm
)
Temperature (K)
(a)
S. Paengson et al./Journal of Materials Science and Applied Energy 4(1) (2015) 9-12
11
280 320 360 400 440 480
1.6
1.8
2.0
2.2
2.4
2.6
1.6
1.8
2.0
2.2
2.4
2.6
6 2(4.93054-0.00927 4.87 10 ) 0.28T T
N-Ca0.97
Bi0.03
MnO3
Temperature (K)
Ele
ctr
ical R
esis
tivity (
mm
)
(b)
Fig. 3. Temperature dependence of the electrical
resistivity for P-Ca3Co4O9 doped Ag and
N-Ca0.97Bi0.03MnO3
Electrical resistivity of P-Ca3Co4O9 doped Ag was depended temperature at 303-473 K as
shown in Fig.3 (a). The electrical resistivity
slowly fluctuation because P-Ca3Co4O9 doped Ag
was mixed phase. Electrical resistivity of N-
Ca0.97Bi0.03MnO3 was depended temperature at
303-473 K as shown in Fig.3 (b). The Seebeck
coefficient of Ca0.97Bi0.03MnO3 values were
linearly decreased with increasing temperature.
280 320 360 400 440 480
6
8
10
12
14
16
18
6
8
10
12
14
16
18
4 2-26.004 0.14 -1.056 10 16.72T T
P-Ca3Co
4O
9 doped Ag
T
herm
al C
onductivity (
W m
-1K
-1)
Temperature (K)
(a)
280 320 360 400 440 4805
6
7
8
9
10
11
5
6
7
8
9
10
11
(b)
5 25.002-0.013 5.052 10 6.07T T
N-Ca0.97
Bi0.03
MnO3
Therm
al C
onductivity (
W m
-1K
-1)
Temperature (K)
Fig. 4. Temperature dependence of the thermal
conductivity for P-Ca3Co4O9 doped Ag and
N-Ca0.97Bi0.03MnO3
Thermal conductivity of P-Ca3Co4O9 doped Ag and N-Ca0.97Bi0.03MnO3 as shown Fig.4 (a)
and (b) respectively. The thermal conductivity of
P-Ca3Co4O9 doped Ag and N-Ca0.97Bi0.03MnO3
were linearly increased with the increasing of
temperature.
280 320 360 400 440 480
0.0
0.7
1.4
2.1
2.8
3.5
4.2
4.9
5.6
N-Ca0.97
Bi0.03
MnO3
P-Ca3Co
4O
9+Ag
Temperature (K)
ZT
x10
-3
Fig. 5. Temperature dependence of the
dimensionless figure of merit for bulks
P-Ca3Co4O9 doped Ag and N-Ca0.97Bi0.03MnO3
The temperature dependent of the
dimensionless figure of merit for P-Ca3Co4O9 doped
Ag and N-Ca0.97Bi0.03MnO3 has a maximum value
at 473 K which evaluated from equation (1)
ZT≈ 0.0038 and 0.0047 respectively.
Temperature decrease triggered by current
0 50 100 150 200 250292.0
292.5
293.0
293.5
294.0
Te
mp
era
ture
(K
)
Time (s)
Heat Absorbed
Heat rejected
Fig. 6. Example Peltier effect relation between
heats absorbed (cold side) heats rejected (hot
side) when used electrical current 0.04 A voltage
0.1 V
When give electrical current to thermoelectric
refrigerator cell a heats absorbed (cold side)
temperature decreased nearly to heats rejected
(hot side) and next time decreasing lowest
temperature in heats rejected (hot side) .The next
a temperature increased because heats rejected
(hot side) can’t rejected heat from cell not enough
and successive. The coefficient of performance
(COP) evaluated by equation (2)
The relationship of coefficient of performance and electrical current at 20-180 mA as shown
Fig.7. Coefficient of performance value at 20-160
mA increased with increasing electrical current
but in 180 mA sharply decreased because oxide
thermoelectric refrigerator cell can’t reject heat
S. Paengson et al./Journal of Materials Science and Applied Energy 4(1) (2015) 9-12
12
from cell not enough and successive influence to
decreased cooling in cold side.
0 20 40 60 80 100 120 140 160 180 2000.30
0.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
0.40
0.30
0.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
0.40
Coeff
icie
n o
f P
erf
orm
ance (
CO
P)
Electrical Current input (mA)
Coefficien of Performance (COP)
Fig. 7. Coefficient of performance (COP) of
oxide thermoelectric refrigerator
CONCLUSION
P-Ca3Co4O9 doped Ag and N-Ca0.97Bi0.03MnO3
were synthesized using solid state reaction method
and P-type and N-type materials shown crystal
structure are orthorhombic. The thermoelectric
properties were Seebeck coefficient and electrical
resistivity shown good thermoelectric properties.
The thermal conductivity is increased because has
doping metal in structure of materials which have
effect to dimensionless figure of merit (ZT) low
value. The coefficient of performance very low
because of Z lowed. However we find a Peltier effect in oxide refrigerator has COP ≈ 0.36
ACKNOWLEDGEMENTS
This research has financially supported by
Thermoelectrics Research Center and Research and
Researcher for Industry (RRi).
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