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

*marta.rull@imm.cnm.csic.es

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