Nano Structured Composite Materials for Thermoelectric Applications

Sung Jin KimSung-Jin KimEwha Womans University

Department of Chemistry and Nano ScienceDepartment of Chemistry and Nano Science

April 5, 2010

Thermoelectricity

연구분야

온도차에 의해 기전력이 발생하는 현상(Seebeck 효과) 또는 전류에 의해 열이 흡수,발생이 생기는 현상(Peltier효과)

응용분야응용분야

열전냉각 (Thermoelectric cooling) 열전발전 (Power generation)

NASNASA

2 www.spaceref.com/news/viewpr.html?pid=18796

Configuration of Thermoelectric ModuleConfiguration of Thermoelectric Module

HEAT INthermoelement

electrical conductor

+

conductorelectrical insulator

p n p n p n p n+−

HEAT OUT

Laser Cooling Modules

Thermoelectric Figure of Merit

Z=α2σ/κ

• Seebeck coeff. (α) : morphology, doping stateEl t i l d ti it ( ) i t ti• Electrical conductivity(σ) : carrier concentration

• Thermal conductivity (κ) : phonon scattering

Optimum Transport Coefficients

Figure of Merit : ZT

S σ=

2S TZTk κ = κ + κ

tot - High Seebeck coefficient

Hi h l t i l d ti itκel

k κ = κe + κph

KL

KL

κ t KL

KL

KL

KL

- High electrical conductivity- Low thermal conductivity

el

κlatt

Difficulties in increasing ZT in bulk materials :

T ato

rs

tals

S ↑ ↔ σ ↓

σ ↑ ↔ S ↓ and k ↑

ZT

1017 1018 1019 1020 10211017 1018 1019 1020 10211017 1018 1019 1020 10211017 1018 1019 1020 10211017 1018 1019 1020 10211017 1018 1019 1020 1021

Insu

l

Met

Semiconductor

5

↑ ↓ ↑10 10 10 10 1010 10 10 10 1010 10 10 10 1010 10 10 10 1010 10 10 10 10Carrier Concentration10 10 10 10 10

Selection Criteria for Candidate Materials

3/2 x ym mT τm = effective massτ = scattering time

( 1/2)max

yrz

latt

T mZ ekγτ

+∝r = scattering parameterklatt = lattice thermal conductivityT = temperatureT = temperatureγ = band degeneracy

Guiding Principles:Guiding Principles:

Narrow band-gap semiconductors : Single carrier systemsHeavy elements : High μ, low κLarge unit cell, complex structure : low κHighly anisotropic or highly symmetricHighly anisotropic or highly symmetricComplex compositions : low κ, complex electronic structureMass Fluctuation : low κHi h d it f t t th F i l l hi h S b k High density of states near the Fermi level : high Seebeck

coefficientScience, 303, 818

New direction : Nano-based Thermoelectrics

• Minimizing the thermal conductivity : Thermal conductivity can be significantly reduced by the scattering of

Interfaces that Scatter

Phonons Electrons

conductivity can be significantly reduced by the scattering of unwanted heat flow at the interfaces

Scatter Phonons but not Electrons

Mean Free Path Λ = 10-100 nm Λ = 1-10 nmWavelength λ = 10-50 nm λ = 1 nm

• Maximizing Seebeck coefficient: Electronic properties may be dramatically modified due to the electron confinement in nanostructures which exhibit low-confinement in nanostructures which exhibit lowdimensional behaviors.

New Classes of Promising Thermoelectric Materials

Nature 413, 597 (2001) Science 297, 2229 (2002) Science 303, 818 (2004)

Ag-Sb–rich

Majumdar, Science 303, 777 (2004) PbSeTe/PbTe QD Super-lattices

AgPb18SbTe20 ZT = 2.2 @ 800K

3.5

3.0

2.5

0K

Super lattices 800K

Science 321, 554 (2008)

N t i l2.0

1.5

1.0

(ZT)3

00

Bulk materials

Nano materials

Year1970 1980 1990 2000 20101950 1960

0.0

1950 1960

0.5 Tl0.02Pb0.98Te ZT = 1.5 @ 773K

Science 320, 634 (2008)Nature 451 168 (2008)

Bulk materials

Sb–richNature 451, 168 (2008)

Nature 459 (2009)

BixSb2-xTe3

NanocompositeIn4Se3 ZT = 1.5 @ 700K

Theoretical studies

Nanodot Nanocomposites Nanograined Nanocomposites

2.52.5

1.81.81 10 L 1.81.8

1.5Λ = 1-10 nm < L

Electron mean free path

Woochul Kim, Yunsei Univ.

New Approach

Nanoparticles Embedded in Bulk Thermoelectric Materials

ElectronPhonon

+ nanorod

nanoparticles

Coherent interface(Matrix/nanoparticles)

nanoparticles

Matrix

Matrix + nanorod, nanoparticles

Type of Bull Matrixes

Nanoparticles Nanorods

Bi2Te3PbTeBi2Te3In2Te3

Bi2Te3Bi2Se3Sb2Te3

BixSb2 xTe3

Bi2Te3CdSe

Te2 3 x 2-x 3Bi

Synthesis of Various NanoparticlesBi(C2H3O2)3

(or Sb(C2H3O2)3)+

1-DodecanthiolOleylamine, 1-Octadecene

75oC 80oC

Size Control

+Te-TOP

(or Se-TOP)

Various reaction temperature

85oC 90oC

M h l C t l

Various Source

Morphology ControlBi2Se3

Composition 140oC

Control

100oC

Bi Bi Te Bi0 9(3)Sb0 9(2)Te3 Bi1 5(3)Sb0 5(1)Te3 Bi1 9(3)Sb0 1(1)Te3

11

Bi Bi2Te3 0.9(3)Sb0.9(2) e3 Bi1.5(3)Sb0.5(1)Te3 Bi1.9(3)Sb0.1(1)Te3

Sample preparation and measurementsSample Preparation

Nanocompositeingot

sawingPolishing

(400 – 2000 - micro)Rocking furnace

800

900

Data AnalysisMeasurements

300 400 500 600 700 800200

300

400

500

600

700

Seebeck Coefficient & Electrical conductivity measurement

Temperature(K)300 400 500 600 700 800

4

5

6

7

conductivity measurement

Nanocomposite sample

Temperature(K)300 400 500 600 700 800

1

2

3

Thermal conductivity measurement

Nano-structured Bulk Thermoelectirc Material

PbTe ingot with Bi2Te3 nanoparticle

+

Bi2Te3 nanoparticles(~150nm)PbTe

incoherent interface

MaterialsLattice

parameterStructure

Lattice mismatch

PbTe 6.3462A Rock salt

PbTe with Bi2Te3

30% (a/a)

Bi2Te3

a=4.385A, c=30.48A

Rhombohedral

2 3

ingot

Nano-Bulk Composite Thermoelectric MaterialPbTe ingot with Bi2Se3 nanoparticle

+

PbTe + Bi2Se3

+

Coherent(stress)

Bi2Se3 nanoparticles(~80nm)PbTe

i h t i t fCoherent(stress) incoherent interface

Nano-Bulk Composite Thermoelectric MaterialIn2Te3 ingot with Bi2Te3 nanoparticle

+coherent interface

(Particle size < 20nm)

In2Te3 Matrix Bi2Te3 nanoparticles(~150nm)(~150nm)

In2Te3 ingot with Bi2Se3 nanoparticle

++coherent interface

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Bi2Se3 nanoparticles(~80nm)

In2Te3 Matrix

Nano-Bulk Composite Thermoelectric Material

Composition dependent of electrical properties

PbTe + 2.7% Bi2Te3 PbTe + 10% Bi2Te3 PbTe + 20% Bi2Te3

Seebeck Coefficient (μV/K) Power Factor (μW/cmK2)Electrical Conductivity (S/cm)

60-40K

)

102 )1200m)

2 3 PbTe + 2.7% bulk Bi2Te3

-160-140-120-100-80-60

ffici

ent (μV

/K

6

8

or (μ

W/c

mK

2

600

800

1000

uctiv

ity (S

/cm

-280-260-240-220-200-180

ebec

k C

oef

0

2

4

Pow

er F

acto

0

200

400

600

trica

l Con

du

250 300 350 400 450 500 550 600 650 700

See

Temperature (K)250 300 350 400 450 500 550 600 650 700P

Temperature (K)300 350 400 450 500 550 600 650 700

0

Elec

t

Temperature (K)

The values : Negative value The values :~1000 S/cm at R.T. Majority of charge carriers :

Electrons The values : ~ -60~-220μV/K

1.5 ~9 W/cmK2

The values : 60 220μV/K

Power Factor increase with decreasing nanoparticle content

Nano-Bulk Composite Thermoelectric Materialte

nsity

Bulk Bi2Te3

* Bi2Te3

* ** *ativ

e in

t

20 30 40 50 60 70 80

* * *

2θ

Rel

asi

ty Nanoparticle Bi2Te3

ve in

tens

20 30 40 50 60 70 80

Rel

ativ

20 30 40 50 60 70 802θ

1 Remove 2 Electrochemically deposition1. Remove barrier oxide layer

2. Electrochemically deposition Bi nanowire material

3. Electrochemically deposition Te nanowire material

4. RemoveAAO templateAAO template

1 Remove 2 Electrochemically deposition1. Remove barrier oxide layer

2. Electrochemically deposition nanowire material

2 Remove1 Remove 2. RemoveAAO template

1. RemoveAg film

•Scheme 1. Schamatic of the process employed to produce (a) superlattice structure (b) one element or binary nanowire arrays by pulsed potentialstructure (b) one element or binary nanowire arrays by pulsed-potential deposition into porous anodic alumina template

SEM image Bi and Te NWs

SummarySummary

열전재료용 나노입자, 나노선 제조 Bulk에 나노입자, 나노선 삽입

Hydrothermal법을 이용한 Bi2Te3의morphologies PbTe ingot with Bi2Te3

Colloidal법을 이용한 Bi2Te3 나노입자

Bi2Se3나노입자

PbTe ingot with Bi2Se3

Sb2Te3 나노입자

BixSb2 xTe3 나노입자

PbTe ingot with Bi2Se3

BixSb2-xTe3 나노입자

Bi 나노입자

InTe ingot with Bi2Se3

CdSe 나노선

전기화학법을 이용한 Bi, Te 나노선

InTe ingot with Bi2Te3

Conclusions

•Nanostructured bulk CompositeTE materialsNanostructured bulk CompositeTE materials- New approaches are promising in raising ZT- Strong thermal conductivity reduction can be achieved through

nanostructuringnanostructuring- Doping studies and processing conditions are important in ZT

optimization

• Nanoparticles- Nano particles of various TE materials are obtained

• Nanocomposites- New approaches was provide to control the size and concentration of the nanocomponent in bulk TE materialsthe nanocomponent in bulk TE materials

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AcknowledgmentAcknowledgmentAcknowledgmentHa Yeong Kim Jieun Park, Hee Jin Kim

Acknowledgment

Dr. Mi-Kyung HanProf. WooChul Kim Yonsei UniversityProf. Wooyoung Lee Yonsei University

Grant:

21st Century Frontier R&D Programs

NRF,

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