high performance zintl phase te materials with embedded ... · 24 a. shakouri 1/4/2011....

Acknowledgement:NSF-DOE,

ONR, DARPA DSO

DOE Thermoelectric Applications Workshop, San Diego; 4 January 2011

Ali Shakouri and Zhixi BianEE, Univ. of California Santa CruzSusan KauzlarichChemistry, Univ. of California DavisIn collaboration withSabah Bux, Jean-Pierre Fleurial; JPLLon Bell; BSST, Amerigon

High performance Zintl phase TE materials with embedded nanoparticles

2

A. Shakouri 1/4/2011

Thermoelectric figure of merit, ZT

TSZTκσ2

=S: Seebeck coefficient

σ: Electrical conductivityκ: Thermal conductivity (e + phonon)

Power factor

Example: Si-doped (InGaAs)0.8(InAlAs)0.2

3


Seebeck-conductivity trade-offEnergy

Density of States

Ef High doping

Doped Bulk Semiconductor

=> Potential to reach ZT~4-5 (with klattice~1W/mK)

Ef Low doping

Deg. Semiconductor/Metal + Energy Filter (Thermionic emission)

Ebarrier

Distance

Deg

. Sem

icon

duct

or/ M

etal

Barr

ier

Energy

Density of States

Ef

D. Vashaee and A. Shakouri, Phys. Rev. Lett. 92, 106103/1 (2004)

4


ErAs Semi-metal Nanoparticles embedded in InGa(Al)As Semiconductor Matrix

Erbium is co-deposited at a growth rate which is a fixed fraction of the InGaAlAs growth rate (MBE growth)

Solubility limit is exceeded → islands are formed (2-3nm ErAs)

Josh Zide, Art Gossard and Chris Palmstrøm (UCSB and Delaware)

ErSb in In0.5Ga0.5Sb

TbAs in GaAs

5


Electrical conductivity and Seebeck (theory/experiment)

M. Zebarjadi, et al., Appl. Phys. Lett. 2009J.-H. Bahk et al., Phys. Rev. B 2010 (Si-doped)J. Zide et al., J. Appl. Phys. 2010

Si-doped InGaAlAs

0.6% ErAs:InGaAlAs Si-doped InGaAlAs

0.6% ErAs:InGaAlAs

Electrical Conductivity Seebeck

The nanoparticle material is not optimized.

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0.08% ErAs

0.6%

Theory

Electron mobility in embedded nanoparticle material

Je-Hyeong Bahk et al. 2010

7

A. Shakouri 1/4/2011Thermal conductivity reduction

Si-doped InGaAlAs

0.6% ErAs:InGaAlAs

UCSB, UCSC, UC Berkeley

8

A. Shakouri 1/4/2011Thermoelectric figure-of-merit

Largest measured ZT~1.33 at 800K

J. Zide et al. Journal of Applied Physics (Dec. 2010)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

300 400 500 600 700 800

ZT

T (K)

ErAs:InGaAlAs

n-InGaAlAs (control)

The majority of ZT enhancement is from thermal conductivity reduction.5% power factor enhancement at 800K.

9


ErAs:InGa(Al)As thick growth approach

63 µm

SEM

Hong Lu, Art Gossard, UCSB

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Nanoparticle scattering optimizationPower factor, n-type InGaAs at 600K

~ 40% enhanced

Optimal: Q=1e, a=1.5 nmBulk alloy

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A. Shakouri 1/4/2011Silicide nanoparticles in SiGe

300K 3.4% nanoparticles

Silicon

Si0.5Ge0.5

GeNiSi2

ZT (300K) ~0.5

ZT (900K) ~1.8

Natalio Mingo et al. Nano Letters 2009

Predictions:

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1THz 10THz

Frequency contributions to thermal conductivity in presence of Iron silicide nanoparticles at 300K

Alloy1nm

3nm

10nm

30nm100nm

300nm

1µm30µm

300µm

Natalio Mingo 2009 (unpublished)

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A. Shakouri 1/4/2011Nanoparticles in Mg2SixSn1-x

Wang and Mingo Applied Physics Letter 2009

Synthesis and Characterization of Mg2Si/Si

Susan Kauzlarich’s GroupTanghong Yi

UC DavisAnd

Jean-Pierre Fleurial’s GroupSabah Bux

JPLPart of this work was performed at the Jet Propulsion Laboratory, California Institute

of Technology under contract with the National Aeronautics and Space Administration.

S. Kauzlarich 1/4/2011

Synthesis Goals

Develop non-toxic Zintl phase magnesium silicide alloys with embedded nanoparticles

Optimizing the matrix alloy composition and the nanoparticles for maximum thermoelectric figure-of-merit in 500K ~ 800K range


Synthesis2MgH2 + (1+x)nano Si(Bi) Mg2Si/xSi(Bi)

(x = 0%, 1.25%, 2.5%, 5%)

Crystallite~ 50 nmParticle size ~200 nm


Powder X-ray Diffraction

2.5 mol% Si5 mol% Si


Transport properties

TY79: MgH2 + bulk Si = 2.25:1TY81: MgH2 + nano Si = 2.2:1TY95: MgH2 + nano Si = 2:1

TY101: MgH2 + nano Si = 1.95:1


Sabah Bux and Jean-Pierre Fleurial (JPL)

0

20

40

60

80

100

120

250 450 650 850 1050

Ther

mal

Con

duct

ivity

(mW

/cm

K)

Temperature (K)

Undoped KidoTY79TY81TY95TY1012% Bi Kido

Tani and Kido, Physica B, 2005, 364, 218-224.

Transport propertiesS. Kauzlarich 1/4/2011

Sabah Bux and Jean-Pierre Fleurial (JPL)

0

20

40

60

80

100

120

250 450 650 850

Latti

ce T

herm

al C

ondu

ctiv

ity (

mW

/cm

K)

Temperature (K)

Undoped Kido

TY79

TY81

TY95

TY101

2% Bi Kido

Nano-Si inclusions (1% to 5%)

Summary and Future Directions

Demonstrated n-type Mg2Si via a new synthetic method (MgH2 + Si) with naturally occurring Si nanoparticle inclusions.

Preliminary measurements of thermoelectric properties by JPL

Carrier concentration changes vs nanoinclusions needs to be studied

Further characterization of the pressed pellets is necessary to determine if the nanoinclusions are isolated and randomly distributed.

Further efforts are underway to reduce particle size along with optimization of carrier concentration.


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PbTe/PbTeSe Quantum DotSuperlattices

Quaternary: ZT=2∆T=43.7 K

T.C. Harman, Science, 2002

Recent Advances in Thermoelectric Materials:Quantum Dot Superlattices (Science 2002), T. Harman et al.

Actual ZT ~1 (see e.g. Nanostructured

Thermoelectrics: Big EfficiencyGains from Small Features,

Vineis et al. Advanced Materials 2010)

Difficulty– Non-active barrier layers: Broido and

Reinecke PRB ‘01, Mahan, etc.

– Improvement “per conduction channel” is 40-60%- Kim et LundstromJ. Appl. Phys. 105, 034506 (2009)

– Dresselhaus et al. 1993

22

A. Shakouri 1/4/2011A. Shakouri 1/21/2010

Solar Cells (Efficiency+ Cost → $/W)

Cronin Vining, Nature Materials 2009

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0

200

400

600

800

1000

1200

1400

1600

1800

2000

1.E+02 1.E+04 1.E+06 1.E+08

Material cost of TE power generation system

Cross over

Air cooling (Aluminum heat sink)

Water cooling (microchannels)

Heat flux [W/m2]

$/m

2

2nd generation TE modules

3rd generation TE modules

K. Yazawa and A. Shakouri, International Mechanical Engineering Congress Nov. 2010

Current TE modules

Today’s TE power generation cost:

$1-2/W

Potential to bring this down to:

$0.1/W

See K. Yazawa’s presentation on

Wednesday

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Acknowledgement

Senior Researchers: Zhixi Bian, Kaz Yazawa, James Christofferson

Postdocs/Graduate Students: Je-Hyeong Bahk, Tela Favaloro, Phil

Jackson, Kerry Maize, Hiro Onishi, Paul Abumov, Oxana Pantchenko,

Amirkoushyar Ziabari, Bjorn Vermeersch, Gilles Pernot, Shila Alavi

Collaborators: John Bowers, Art Gossard, Chris Palmstrom (UCSB),

Tim Sands (Purdue), Rajeev Ram (MIT), Venky Narayanamurti

(Harvard), Arun Majumdar (Berkeley), Josh Zide (Delaware),

Lon Bell (BSST), Natalio Mingo (CEA/UCSC), Susan Kauzlarich (Davis),

Sabah Bux, Jean-Pierre Fleurial (NASA JPL)

high performance zintl phase te materials with embedded ... · 24 a. shakouri 1/4/2011....

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