Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

Class 12: Thermoelectrics

Peltier Effect

I+-

Active Cooling

Heat Rejection

np

Refrigeration Mode Power Generation Mode

I

Heat Source

Heat Sink

np

Seebeck Effect

“Refrigeration without movingparts and chemical refrigerant”

“Electricity from waste-heat”

Solid State materials are the key

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

66% 34%Energy Used

Electrical Energy

Automobile

Nuclear Power Plant

Waste Incinerator

Factory

Natural GasThermal Power Plant

PrimaryEnergy

RetrievalEnergy Loss/Waste Heat

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

Guest Editors: Tritt and Subramanian

March 2006

Thermoelectric Materials, Phenomena, and Applications: A Bird's Eye View: T. M. Tritt, M. A.Subramanian

Recent Developments in Bulk Thermoelectric Materials:G. S. Nolas, M. Kanatzidis

Properties of Nanostructured One-Dimensional and Composite: Thermoelectric Materials : A. M. Rao, X. Ji, and T. M. Tritt

March 2006

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl

10171018 1019 1020 1021

α σ

Carrier Concentration

Tota

l ΚZT

insu

lato

r

met

al

semiconductor

Contra-indicatedProperties

σ 2

ZT =α

(κe + κL)• T

Seebeck coefficientor thermopower

(ΔV/ΔT)

Electrical conductivity

Total thermal conductivity

σ α2α

σ

κ

ZTmax

κL

κe

No upper limit for ZT

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

+ +

Glass (amorphous)Very low

thermal conductivity

MetalHigh

electrical conductivity

Semiconductor High

Thermopower

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

25 450

1.0

- 75- 200Temperature oC

ZT

Bi2Te3 alloysPbTe alloys Si0.7Ge0.3

850

Narrow band gap semiconductors (increasing numerator)Elements of high atomic weight – e.g. Bi, Pb, Hg, Te (decreasing the denominator)

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

CsBi4Te6:Kanatzidis et al., Science, 287, 1024(2000)

AgPbmSbTe2+m:Kanatzidis et al., Science, 303, 818 (2004)

In0.2Co4Sb12:Subramanian et al., Chemistry of Materials, 18, 759 (2006)

Yb0.19Co4Sb12:Nolas, Tritt et al., J. Appl. Phys. 97, 113715 (2005).

In0.2Co4Sb12Ag

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

Co4Sb12 RxCo4Sb12 (R = Rare-earth, In)Large numeratorLarge DenominatorZT ~ 0.4 at 600K

Large numeratorSmall denominatorZT~ 1.3 at 600K

Subramanian et al., Chemistry of Materials, 18, 759 (2006)Nolas, Tritt et al., J. Appl. Phys. 97, 113715 (2005)Singh et al., Phys. Rev. B 53, 6273 (2003)

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl

Intermetallics with rare earths in intermediate valence statesYb 2+,3+ (4f13-4f14) ; Ce 3+,4+ (4f1-4f0)Large Density of States at the Fermi Level

- interaction between conduction electrons and partially localized 4f electrons leads to large α

- very large numerator (power factor) - large denominator (thermal conductivity) – low ZT

YbAl3 and CePd3

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl

PbSe

Bulk PbTe

•Electronic properties may be dramatically modified due to carrier confinement in nanostructures

•Thermoelectric power enhancement (rippling effect on DOS)

FEE

dEEd

eTkS B

==))((ln

3

22 σπ

PbSe

α

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl

AgPb18SbTe20Ag

Sb

Te

Pb

0

0.5

1

1.5

2

2.5

300 400 500 600 700 800

Latti

ce T

herm

al C

ondu

ctiv

ity (W

/mK

)

Temperature (K)

PbTe

LAST-18

Lattice thermal conductivity

Power factor still high

nanostructure

Kanatzidis et al Science, 2004, 303, 818

Class 12: Thermoelectrics

Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrlThese ppt slides were created by Professor M. A. Subramanian, Oregon State.

Pb Te Pb Te Pb Te Pb

Te Pb Te Pb Te Pb Te

Pb Te Sb Te Pb Te Pb

Te Ag Te Ag Te Pb Te

Pb

Te Pb

Te

Te

Sb

Pb

Te

Te

Pb

Pb

Te

Te

Pb

Ag Te Pb Te Pb Te Pb

Te Pb Te Pb Te Sb Te

Pb Te Pb Te Pb Te Pb

Te Ag Te Pb Te Pb Te

Pb

Te Pb

Te

Te

Pb

Pb

Te

Te

Sb

Pb

Te

Te

Pb

Dissociated state..unstable

Associated state..stable

Class 12: Thermoelectrics