Nanostructured Thermoelectric Materials: From Basic ... · Nanostructured Thermoelectric Materials:...
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– – WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT Nanostructured Thermoelectric Materials: From Basic Physics to Applications Gang Chen Nanoengineering Group Rohsenow Heat and Mass Transfer Laboratory Massachusetts Institute of Technology Cambridge, MA 02139 Email: [email protected] http://web.mit.edu/nanoengineering Acknowledgments: J.P. Fleurial DOE, NSF, and Industry
Transcript of Nanostructured Thermoelectric Materials: From Basic ... · Nanostructured Thermoelectric Materials:...
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Nanostructured Thermoelectric Materials: From Basic Physics to Applications
Gang Chen
Nanoengineering GroupRohsenow Heat and Mass Transfer Laboratory
Massachusetts Institute of Technology
Cambridge, MA 02139
Email: [email protected]://web.mit.edu/nanoengineering
Acknowledgments:J.P. Fleurial
DOE, NSF, and Industry
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Outline
•
Why nanocomposites?•
What we have achieved?
•
What we do not understood?•
Application opportunities
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Nanoscale Effects for Thermoelectrics
Phonons=10-100 nm
=1 nm
Electrons=10-100 nm=10-50 nm
Electron Phonon
Interfaces that Scatter Phonons but not Electrons
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
0
20
40
60
80
10 1 10 2 10 3 10 4
THER
MA
L C
ON
DU
CTI
VITY
(W/m
K)
LAYER THICKNESS (Å)
BULK
SPECULAR (p=1)
p=0.95
p=0.8DIFFUSE (p=0)
Yao (1987)Yu et al. (1995)0
20
40
60
80
10 1 10 2 10 3 10 40
20
40
60
80
0
20
40
60
80
10 1 10 2 10 3 10 410 1 10 2 10 3 10 4
THER
MA
L C
ON
DU
CTI
VITY
(W/m
K)
LAYER THICKNESS (Å)
BULK
SPECULAR (p=1)
p=0.95
p=0.8DIFFUSE (p=0)
Yao (1987)Yu et al. (1995)
Heat Conduction Mechanisms in Superlattices
Periodic Structures Are Not Necessary, Nor Optimal!
Major Conclusions:
•
Ideal superlattices do not cut off all phonons due to pass-bands
•
Individual interface reflection is more effective
•
Diffuse phonon interface scattering is crucial
10-1
100
101 102 103
Capinski et al. 1999Capinski et al. 1999
Yao 1987 Yu et al. 1995
Nor
mal
ized
The
rmal
Con
duct
ivity
Period Thickness (Å)
T=300KAlAs/GaAs
In-Plane
Cross-Plane
LD
LD
Ideal Superlattices
In-Plane
Cros
s-Pl
ane
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Nanocomposites Approach
–
Increase interfacial scattering by mixing nano-sized particles.
–
Enable batch fabrication for large scale application.
Nanoparticle(a) (b)
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Low-Cost Synthesis
AGraphite cylinder
Graphite piston
Current for heating
Force for pressing
Sample powder A
Graphite cylinder
Graphite piston
Current for heating
Force for pressing
Sample powder
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Thermoelectric Properties: Bi2
Te3
Poudel et al., Science, 320, 634, 2008
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Six
Ge1-x
System
Joshi et al., Nano Letters 8, 4670 (2008)
Wang, et al.
Appl. Phy. Lett. 93, 193121 (2008)
P-type SiGe
N-type SiGe
0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 RTG SiGe Si80Ge20B5 (run-1) Si80Ge20B5(run-1)- annealed 7 days Si80Ge20B5(run-2)
ZT
Temperature ( oC)
0
5
10
15
20
25
30
35
40
45
200 400 600 800 1000 1200 1400
Ther
mal
Con
duct
ivity
(W.m
-1K-1
)
Temperature (K)
No large cold welded agglomeratesShort Pressure Sintering at 1275 KLong Pressure Sintering at 1475 K
Undoped SiSingle Crystal
Doped Nanobulk Si using only "cold
welded" agglomerates of nanoparticles
Undoped Nanobulk Si
Doped Nanobulk Si
Bux et al., Adv. Func. Mat., 2009
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Understanding Electron and Phonon Transport in Random Nanostructures
5 nm
Phonons: •
What is the mean free path in bulk materials Phonon-phonon Dopants Alloy Electron scattering Defects
•
How phonons are scattered at an interfaces Interface roughness Crystallographic directions Anharmonic effect
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Molecular Dynamics Simulation of Phonon Mean Free Path
10-3
10-2
10-1
100
101
102
103
0
10
20
30
40
50
60
70
80
90
100
Mean Free path (m)
Per
cen
t A
ccu
mu
lati
on
CallawayAseMD
Henry and Chen, J. Comp. Theo. Nanosci., 5, 141 (2008).
Si
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.00
0.05
0.10
0.15
0.20
0 30 60 90
SV
TO
SV
WA
VE S
V TO
L WA
VE
INCIDENT ANGLE (DEGREE)
REFLECTIVITYTRANSMISSIVITY
REFLECTIVITY
TRANSMISSIVITY
Interface Reflectivity and Transmissivity
L(v)1(v)2
sv
L
svsv
We know how to do it only in the continuum limit, with perfect interfaces!
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Thermal Interface Resistance Between Perfectly Contact Solids
Cahill et al., JAP, 2003
•
No model can predict interface thermal conductance except at very low temperatures.
•
Phonon transmissivity and reflectivity at interfaces are crucial parameters to model heat conduction in thermoelectric materials.
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Electron Transport
•
Where thermoelectric effect happens?
•
Interfacial barrier height
•
Momentum conservation at interfaces
•
Scattering inside particles
•
Energy dependency of scattering
5 nm
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Thermionic emission at grain boundaries
SiGe nanocomposite,
Eb
=0.2eV, ND
=4x1020
cm-3
Need: Em
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Nanoparticle/Nanograin Scattering
D/2carrier
Dominant electron wavelengths
* ~ 6 10nmc
hm v
Grain size
m~ 20 n30D
Grain boundary thicknessm~1ntDebye screening length
1/2
2 ~ 0.5 m1 nDkTLe N
Nanograin
D/2D/2carrier
Dominant electron wavelengths
* ~ 6 10nmc
hm v
Grain size
m~ 20 n30D
Grain boundary thicknessm~1ntDebye screening length
1/2
2 ~ 0.5 m1 nDkTLe N
Dominant electron wavelengths
* ~ 6 10nmc
hm v
Grain size
m~ 20 n30D
Grain boundary thicknessm~1ntDebye screening length
1/2
2 ~ 0.5 m1 nDkTLe N
Nanograin
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Electrons: MFP vs λ
5 10 15 20 25 301
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
MF
P (
nm
)
Electron wavelength (nm)
Minnich et al., Energy & Env. Sci., 2009.
SiGe
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Potential Applications
Industrial Waste Heat (DOE/ITP)
Renewables
Transportation
Main AC: TE Local cooling of seats: TE
Catalytic converter: TE
Radiator: TE
Main AC: TE Local cooling of seats: TE
Catalytic converter: TE
Radiator: TE
BuildingsCombustor: TE
Solar Panel: PVSolar Panel: PV
Furnace: TE
Refrigerator
HVAC: TE
And Entropy is Generated
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
System Consideration
TobjectTcold
Thot
TambientT
Tte
Sometimes, thermal systems more expansive
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Heat to Electricity Recovery from Gas Stream
Hot Gasm, Th
,i
Hot GasTh
,o
Heat Transfer Surfaces
Coolant
InsulationHot Side TemperatureTH
Cold Side TemperatureTc
•
For thermoelectric devices, TH
higher is better•
However, maximum heat intercepted from hot gas stream, mcp
(Th,i
-TH
), decreases with TH
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
Efficiency Expectations• Th,i
=600 oC, Tc
=50 oC• Optimal Hot Side Temperature ~ 270 oC
0
0 . 0 5
0 . 1
0 . 1 5
0 . 2
0 . 2 5
0 . 3
0 .5 1 . 5 2 . 5
F I G U R E O F M E R I T ZT
EFF
ICIE
NCY
Ideal Device 50-600 oC
Ideal Device ~50-270 oC
Line: System Efficiency 50-270 oCDots: System Efficiency 50-250 oC
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
0
0.05
0.1
0.15
0.2
0.25
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0.5 1 1.5 2 2.5 3
EFFI
CIE
NC
Y
FIGURE OF MERIT ZT
Ideal Device 50-600 oC
Ideal Device 50-270 oC
Line: System Efficiency 50-270 oCDots: System Efficiency 50-250 oC
Ideal System
0
0.05
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0.15
0.2
0.25
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0.5 1 1.5 2 2.5 3
EFFI
CIE
NC
Y
FIGURE OF MERIT ZT
0
0.05
0.1
0.15
0.2
0.25
0.3
0.5 1 1.5 2 2.5 3
EFFI
CIE
NC
Y
FIGURE OF MERIT ZT
Ideal Device 50-600 oC
Ideal Device 50-270 oC
Line: System Efficiency 50-270 oCDots: System Efficiency 50-250 oC
Ideal System
Locally Optimized Systems
TEG2
T2
TEG3
T3
TEG1
T1
TEG2
T2
TEG3
T3
TEG1
T1
Hot Gas • 1-3% Absolute Efficiency• Engineering Room• Materials Development
––WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MITWARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY, MIT
![Recent Progress in Nanostructured Thermoelectric Materials · nanoscale [3]. Until now, two di erent approaches have been investigated to search for high ZT thermoelectric materials](https://static.fdocuments.net/doc/165x107/5f2b985c1c26767db73835f6/recent-progress-in-nanostructured-thermoelectric-nanoscale-3-until-now-two-di.jpg)
