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Marta Rull-Bravo1,*, Alberto Moure2, Begoña Abad2, Miguel Muñoz Rojo2, Alexander Jaquot3, Adolfo del Campo2,
José Francisco Fernández2, Marisol Martín González1
Tailoring the thermoelectric properties of Skutterudites by nanocomposites
1Microelectronics Institute of Madrid, CSIC, 28760 Tres Cantos, Madrid, Spain 2Instituto de Cerámica y Vidrio, CSIC, 28049, Madrid, Spain
3Fraunhofer-IPM, 79110 Freiburg, Germany
34th ANNUAL INTERNATIONAL CONFERENCE ON THERMOELECTRICS
13th EUROPEAN CONFERENCE ON THERMOELECTRICS
Skutterudites have attracted great attention for their promising potential
on thermoelectric applications, such as harvesting the heat generated in industrial processes and automotive
operations. To improve their thermoelectric figure of merit ,emphasis has gone into modifying the band structure
through doping to enhance the Power Factor and reducing thermal conductivity through increasing phonon
scattering by filling and in-situ nanocomposites formation.1 Depending on the nature of the nanoinclusions and the
proportion in the matrix, it is possible to tailor the thermoelectric properties.2
In this work, different concentrations of oxides were included in a one-step synthesis mechanism, obtaining the
Skutterudite phase with nanoinclusions and therefore, achieving lower thermal conductivities than those reported in
literature.
Synthesis of CoSb3-alloys were performed by High Energy Ball Milling and compaction by Spark Plasma Sintering, resulting in the formation
of a cobalt antimonide nanocomposite.
The high amount of interfaces achieved increases the phonon scattering and reduces the thermal conductivity to values around 2 Wm-1K-1. Doping with tellurium increases the power factor. By using both approaches together, the thermoelectric properties are highly increased by effective decoupling of thermal and electrical properties.
Acknowledgements:
European Commission under the Seventh Framework Programme (FP7) Grant # 263167
References: [1] Shi, X. et al. Multiple-Filled Skutterudites: High Thermoelectric Figure of Merit through Separately Optimizing Electrical and
Thermal Transports. Journal of the American Chemical Society 133, 7837-7846 (2011)
[2] Zhao, X. et al. Synthesis of Ybyco4sb12/Yb2o3 Composites and Their Thermoelectric Properties. Applied Physics 6, 89, 092121 (2006)
[3] Rull-Bravo,M. et al. Skutterudites as Thermoelectric Materials: Revisited. RSC Advances 5, 41653-41667 (2015)
1995 2000 2005 2010 2015
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
zT
Year
n-type
p-type
Reduce k by nanocomposites
segregation
Increase S2s by doping
State of the art in Skutterudites3
Sb
Te
d1 d2
d1 d2
Approaches to enhance CoSb3 figure of merit
20 30 40 50 60 70 80
Inte
nsi
ty (
a.u
.)
2 (degree)
0 h
1 h
4 h
6 h
14 h
15 h
552
550
44463
162
253
244
2433
431
422
33242
0
330
321
310
211
CoSb3● Sb2O3 ◊ CoSb2
● ◊ ◊
5.0 μm
100 200 300 400 500 600 700 800
Inte
nsi
ty (
a. u
.)
Raman shift (cm-1)
CoSb3
CoSb2O4
Sb2O3+CoSb
3
Eg
Ag
TgT
gAg
Tg
Tg
X-Ray diffraction and Raman confirm the presence of CoSb3 phase and CoSb2O4
and Sb2O3 as secondary phases.
Nanostructuring in the nanopowder was confirmed by TEM images.
CoSb3 phase and oxide segregation and their different electrical conductivity
behaviors were confirmed with topographical and current maps measured by AFM.
300 400 500 600 700 800 9000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
zT
Temperature (K)
CoSb3
x=0,05
x=0,15
x=0,2
300 400 500 600 700 800 9001.6
2.0
2.4
2.8
3.2
3.6
4.0
4.4
4.8
CoSb3
Th
erm
al co
nd
uctivity (
W/m
.K)
Temperature (K)
x=0,15x=0,2
x=0,05
300 400 500 600 700 800
0.0015
0.0020
0.0025
0.0030
0.010
0.015
0.020
x=0,1
x=0,15
CoSb3
Re
sis
tivity (
c
m)
Temperature (K)
x=0,05
x=0,2
300 400 500 600 700 800 900-400
-360
-320
-280
-240
-200
-160
-120
-80
-40
CoSb3
Se
eb
eck c
oe
ffic
ien
t (
V/K
)
Temperature (K)
x=0,2
x=0,15
x=0,05
x=0,1
300 400 500 600 700 8000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Temperature (K)
zT
CoSb3 nanocomposite
CoSb2,85
Te0,15
300 400 500 600 700 80010
-3
10-2
0
2
4
6
8
CoSb2.85
Te0.15
nanocomposite CoSb3
CoSb2.85
Te0.15
Temperature (K)
Re
sis
tiv
ity
(
·cm
)
nanocomposite CoSb3
Th
erm
al c
on
du
ctiv
ity (W
/(m
.K))
Thermoelectric properties of Te-doped CoSb3 nanocomposite CoSb3-xTex
zT=1
Decoupling electrical and thermal conductivity, through doping and
nanostructuring, leads to an enhance the figure of merit.
For CoSb2.85Te0.15 compound a zT of 1.0 at 750K is achieved.
0.00
-99.42
0.00nA
-99.42nA
X-Ray diffraction SEM/TEM Optical image Raman C-AFM