M.Rull-Bravo 1, A. Moure 2, B. Abad 1, M. Muñoz 1, A. Jacquot 3, J.F. Fernández 2, M. Martín-González 1

25/9/2014

1 Dept. Biosensores, Instituto de Microelectrónica de Madrid, C/Isaac Newton 8, 28760, Tres Cantos, Spain. 2 Dept. Electrocerámica, Instituto de Cerámica y Vidrio, C/ Kelsen, 5 Madrid 28049, Spain. 3 Thermoelectric Systems department, Fraunhofer-IPM, Heidenhofstraße 8, 79110 Freiburg,Germany.

Outline

Introduction Objectives Experimental results CoSb3 reference sample Doped samples

Ni-doped CoSb3

Te-doped CoSb3

Conclusions

1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8 p-type n-type nanocomposite

zT

Publication year

In0.2Ce0.15Co4Sb12

DD0.65Fe3CoSb12

Ba0,08La0,05Yb0,04Co4Sb12

Yb0.26Co4Sb12/0.2GaSb

Introduction

Chemical formula MX3 M=Co,Rh,Ir X=P,As,Sb

CoSb3 ↔ 2Co8Sb24 ↔ Co4Sb12 Two approaches:

•Filled and doped skutterudites •Nanocomposites

Alleno et al, Journal of Electronic Materials, Vol. 39, No. 9, (2010) B. Poudel et al, Science, Vol. 320, 634 (2008)

ZT= S2σ

κe+ κph T

zT ~1.4 at 373K 3D nanobulk (Bi,Sb)2Te3

↑S2σ ↑ κe+ κph

Objectives

Site A Site B

AB3

ZT= S2σ

κe+ κph T

Thermal conductivity reduction with CoSb3 nanocomposites.

κ

+ Increase of S2σ through doping

CoSb3 nanocomposite

PATENT PENDING

Nanocomposite Lower thermal conductivity (κ=2.8 at 573K)

Necessary to optimize σ doping Optical image of the composite

CoSb3 nanocomposite

300 400 500 600 700 800-450-400-350-300-250-200-150-100-50

050

100

Seeb

eck

coef

ficie

nt (µ

V/K)

Temperature (K)

Liu et al

CoSb3 nanocomposite

300 400 500 600 700 8000,00

0,01

0,02

0,03

0,04

0,05

0,06

0,07

Resis

tivity

(Ω.c

m)

Temperature (K)

Liu et al

CoSb3 nanocomposite

300 400 500 600 700 800

2,5

3,0

3,5

4,0

4,5

5,0

5,5

Ther

mal

con

duct

ivity

(W/(m

.K2 ))

Temperature (K)

Liu et al

CoSb3 nanocomposite300 400 500 600 700 800

0,000,020,040,060,080,100,120,140,160,180,200,22 CoSb3 nanocomposite

Liu et al

zT

Temperature (K)

W-S,Liu et al, J. Phys. D: Appl. Phys. 40 (2007) 566–572

20 30 40 50 60 70 80

Co0,85Ni0,15Sb3

SPS

Inte

nsity

(a.u

.)

2θ (degree)

6 h14 h

4 h

2 hRef.

Sb

Ni-doped samples Physico-chemical characterization

Th.Formula Exp. Formula

SPS-Co0,95Ni0,05Sb3 Co0,88Ni0,034Sb2,7

SPS-Co0,85Ni0,15Sb3 Co0,82Ni0,12Sb3,05

SPS-Co0,7Ni0,3Sb3 Co0,64Ni0,29Sb3,07

EDS of the Ni-doped samples

XRD patterns of the milling process and SPS

20 nm

TEM of the CoSb3 nanopowder

Ni-doped samples Physico-chemical characterization

73.75nm

0.00nm

0.00nA

-99.42nA

Topographical map Current map 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0

50

100

150

200

250

Num

ber o

f cou

nts

Non conductive grain area (µm2)

Frequency counts of Co0,85Ni0,15Sb3

V I Non-conductive average area of 13.6%

Statistical study with ImageJ

300 400 500 600 700 800

2,0

2,5

3,0

3,5

4,0

4,5

5,0

Ther

mal

con

duct

ivity

(W/m

.K)

Temperature (K)

x=0,3

x=0,15x=0,05

CoSb3

300 400 500 600 700 800 900

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9zT

Temperature (K)

CoSb3

x=0,3

x=0,15x=0,05

300 400 500 600 700 8000,000

0,002

0,004

0,0060,0080,0100,0120,0140,0160,0180,020

Resis

tivity

(Ω c

m)

Temperature (K)

CoSb3

x=0,3x=0,15

x=0,05

Ni-doped samples Thermoelectric properties

300 400 500 600 700 800-400

-360

-320

-280

-240

-200

-160

-120

-80

-40

0

CoSb3

x=0,15

x=0,05

Seeb

eck

Coef

ficie

nt (µ

V/K)

Temperature (K)

x=0,3

Reactives zT CoSb3 0.16@573K

Co0.95Ni0.05Sb3 0.61@787K Co0.85Ni0.15Sb3 0.60@787 K Co0.7Ni0.3CoSb3 0.44@787 K Co1-xNixSb3

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40

50

100

150

200

250

300

350

Num

ber o

f cou

nts

Non-conductive grain area (µm2)

Frequency counts of CoSb2,85Te0,15

20 30 40 50 60 70 80

Ref.

CoSb2,8Te0,2

SPS

16 h

Inte

nsity

(a.u

.)

2θ (degree)

0 h

Te-doped samples Physico-chemical characterization

Topographical map Current map

XRD patterns of the milling process and SPS

Sb

Non-conductive average area of ~20% Statistical study with ImageJ

300 400 500 600 700 800 9000,00,10,20,30,40,50,60,70,80,91,01,1

zT

Temperature (K)

CoSb3

x=0,05

x=0,15x=0,2

300 400 500 600 700 800 900

0,002

0,004

0,006

0,008

0,010

0,012

0,014

0,016

0,018

0,020

CoSb3

Resis

tivity

(Ω.cm

)

Temperature (K)

300 400 500 600 700 800

0,0015

0,0020

0,0025

0,0030

0,0035

Resis

tivity

(Ω.cm

)

Temperature (K)

x=0,15x=0,1x=0,2

x=0,05

Te-doped samples Thermoelectric properties

Reactives zT

CoSb3 0.16@573K

CoSb2,95Te0,05 0.7 @814K

CoSb2,85Te0,15 0.7 @738K

CoSb2,8Te0,2 0.8 @739K

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

Ther

mal

con

duct

ivity

(W/m

.K)

Temperature (K)

x=0,15x=0,2

x=0,05

300 400 500 600 700 800 900-400

-360

-320

-280

-240

-200

-160

-120

-80

-40

CoSb3

Seeb

eck

coef

ficie

nt (µ

V/K)

Temperature (K)

x=0,2

x=0,15

x=0,05

x=0,1

CoSb3-xTex

Te-doped samples Thermoelectric properties

Reactives zT

CoSb3 0.16@573K

CoSb2,8Te0,2 0.8 @739K

CoSb2,8Te0,2 1.0 @791K CoSb2.8Te0.2

300 400 500 600 700 8000,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

zT

Temperature (K)

nca ~ 8%

nca ~ 20%

300 400 500 600 700 8000,00080,00100,00120,00140,00160,00180,00200,00220,00240,00260,00280,0030

Resis

tivity

(Ω.c

m)

Temperature (K)

nca ~ 8%

nca ~ 20%

300 400 500 600 700 8001,71,81,92,02,12,22,32,42,52,62,72,82,93,03,13,23,3

Ther

mal

con

duct

ivity

(W/m

.K)

Temperature (K)

nca ~ 8%

nca ~ 20%nca= non-conductive area

300 400 500 600 700 800-240

-220

-200

-180

-160

-140

-120

nca ~ 20%Seeb

eck

coef

ficie

nt (µ

V/K)

Temperature (K)

nca ~ 8%

Nanocomposite skeleton seems to

improve the stability of the

Te-Doped Skutterudites

Conclusions

A new processing route combining a high energetic milling and Spark Plasma Sintering at reduced temperatures (600ºC) is used to obtain CoSb3 nanocomposite.

The high amount of interfaces achieved by the nanostructuration increases the phonon scattering and reduces the thermal conductivity.

High figure of merit have been obtained with Ni or Te-doped samples.

Nanocomposite skeleton seems to improve the stability of the Te-Doped Skutterudites

Thank you for your attention

Acknowledgements:

European Commission under the Seventh Framework Programme (FP7) since July 2011. Grant # 263167

Introduction: methods Processes to prepare nanosized powders:

• Rapid solidification • Sprying • Solution chemistry • Fast quenching • High energy milling

Consolidation techniques: • Hot Pressing • Spark Plasma Sintering

Nanostructuration Higher densification Microstructure or nano/micro mixture (composite)

Te-doped samples Thermoelectric properties

Reactives zT

CoSb3 0.16@573K

CoSb2,95Te0,15 0.7 @738K

CoSb2,85Te0,15 1.3 @791K CoSb2.85Te0.15

300 400 500 600 700 8000,00110,00120,00130,00140,00150,00160,00170,00180,00190,00200,00210,0022

Resis

tivity

(Ω.c

m)

Temperature (K)

nca ~10%

nca ~20%

300 400 500 600 700 800

-220

-200

-180

-160

-140

-120

nca ~10%

Seeb

eck

coef

ficie

nt (µ

V/K)

Temperature (K)

nca ~20%

300 400 500 600 700 800

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

3,0

3,2

3,4

Ther

mal

con

duct

ivity

(W/m

.K)

Temperature (K)

nca ~20%

nca ~20%

300 400 500 600 700 8000,00,10,20,30,40,50,60,70,80,91,01,11,21,31,41,51,61,71,8

zT

Temperature (K)

nca ~10%

nca ~20%

EDS of Te-doped samples

Th.Formula Exp. Formula

CoSb2,95Te0,05 Co0,96Sb3,01Te0,03

CoSb2,9Te0,1 Co0,92Sb2,93Te0,07

CoSb2,85Te0,15 Co0,92Sb2,92Te0,15

CoSb2,8Te0,2 Co0,96Sb2,88Te0,16