Role of structures on thermal conductivity in thermoelectric - - PDF document

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 1

Role of structures on thermal conductivity in thermoelectric materials

• C. Godart, A.P. Gonçalves, E.B. Lopes,
• B. Villeroy, E. Alleno, O. Rouleau

CNRS UMR7182- ICMPE / CMTR- Thiais, France

• Dep. Química, I.T.N.- Sacavém, Portugal

Acknowledgments: Franco-Portuguese Program GRICE N° 20157 (2007-2008) Thanks to Velijko

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 2

Recent evolutions 2007: CNRS GDR TE (founding labs: Bordeaux, Caen, Montpellier, Nancy, Thiais) LOCIE (building) Industrials join the meetings program "Energie 2" (CNRS) Hope it will help to include "thermoelectric" word in 7th PCRD 2008: 140 participants in European TE Conf. publications on line: (http://ect2008.icmpe.cnrs.fr/)

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 3

OUTLINE

* Crystallography bonding, distances, cages

ZT, σ, S, semiconductor λ Thermal conductivity: electronic λél lattice λlatt,

* Classical TE materials (semiconductor) * Various effects of structure to decrease λlatt

ADP - few cage like structures Few complex structures

* Conducting glass (Gonçalves)

Micro composites Nano materials (1, 2D) Nano composites

* Shaping (SPS) - applications

Properties and Applications

• f Therm oelectric Materials

HVAR 2 0 0 8 Applications Applications Applications new Nano Sales

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 4

NaCl F (225) FCC compact a= 5.64 CsCl P (221) CC non compact a=6.17

Cl Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Cl

Cl Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Na Cl Cl Cl Na Na Cl

a b c Cl Cl Cl Cl Cs Cl Cl Cl Cl

a b c Cl Cl Cl Cl Cs Cl Cl Cl Cl

Coordinence 8 6 No atom1 atom2 distance

• 1

Cl Na 2.8200 2 Na Na 3.9881 No atom1 atom2 distance

• 1

Cl Cs 3.5707

Structure - bonding

Distances between atoms

• (distance (A1-A2)- radius A2) >> radius A1 : possibility of cage around A1
• different distances around atom A on sites 1 , 2 : possibility of cage

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 5

Atomic Displacement Parameters (ADP)

atom A (T≠0) moves atomic displacement parameter : mean square displacement amplitudes / equilibrium generally non isotropic Uij (ellipsoids of movement of the atoms) mean value in all directions Uiso (check atoms with strong vibrations) Uiso (T) ↑ si T ↑ if Uiso (T->0) ≠ 0: possibility of static disorder

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 6

I => Q Q = Π . I cooling

Seebeck (S) 2 TE effects (1822 à 1850) Peltier (Π)

XXX

Thompson (Lord Kelvin) Π = S . ∆ T = Q / I ∆T=Tc-Tf

∆T => ∆V ∆V = S. ∆T electricity generation thermocouple Tc Tf S: Seebeck coefficient = entropy per charge carrier / charge, N(EF)

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 7

TE Couple 2 materials: type p & type n

Heat sink Tc Hot zone Th

e- h+ I Load h+

Cold Tc Hot zone Th

e- I Cooling Generation Heat Flux

Device: chemically loving materials

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 8

maximum of ZT = S2 σ T / λ Optimize transport properties of materials Cooling:

( )( )

γ γ + − − = 1 T T T T COP

h c h c

electricity generation :

( )( )

T T T T

h c c h

γ γ η + − − = 1

max

γ = (1+ZT)1/2

1- increase the power factor : S2 σ

S decreases ~ log (n, p) σ increases ~ (n,p)

10 14 1016 1018 10 20 10 22 Semiconducteur Métal Isolant

S2σ σ S

Carrier content

Semiconductor

FIGURE of MERIT ZT)

2- decrease the thermal conductivity : λ λ= λél + λ latt

DO NOT affect σ

Play on phonons

GOOD electric conductor BAD thermal conductor!!

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 9

Effects on phonons Materials Complex structure Increase the optical phonons modes (heat carried by 3 acoustic modes & less by 3(N-1) optical modes Clathrate Chevrel (SC) Intermet.Yb14MnSb11 Skutterudite Weakly bound atoms (or out of positions ) Increase disorder Skutterudite Clathrate Penta-telluride Solid solutions, vacancies Increase mass fluctuations + half Heusler Impurities, inclusions Increase diffusion Bi2Te3+Te+CuBr Zn4Sb3 PbTe -TAGS composites Grains boundaries Reduce the mean free path of phonons Nano-materials (PbTe+TAGS), low dimensionality

• G. Slack, TE handbook 1995

see A.P. Gonçalves, Conducting glass- Hvar 2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 10

Thermoelectric materials (from inefficient to better..)

Known Systems in 1960 …& in 1990 !!!

Semicond. Bi-Sb (Bi,Sb)2 (Te,Se)3 PbTe TeAgGeSb Si-Ge T use (K) 200 ~300 /GAP/ 700 750 ~1000 ZT at T use 1.1 (H) 0.9 0.8 1.1 0.6

Materials: 1-better ZT 2-stable at T ↑ 3-ZT ↑ in [T] ↑

200 400 600 800 1000 1200 5 10 15 20 25 30 35 ZT ZT=3.5 ZT=3 ZT=2.5 ZT=2 ZT=1.5 ZT=1

∆T

Efficacité Maximum η (%) Température chaude (K)

Cooling electricity generation

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 11

Thermoelectric materials (1960-90.. ) & ZT ≈ 1

• 200

200 400 600 800 1000 1200 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 (Si,Ge) PbTe TeAgGeSb (Bi,Sb)2 (Se,Te)3 ZT T (°C)

T gap

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 12

New: Zn4Sb3 skutterudites complex clathrates Chevrel Oxides 200 400 600 800 1000 1200 1400 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Godart- CNRS- 2008

CuMo6Se8 Yb14MnSb11 NaxCoO2 Ca3 -xNaxCo4O9 Ba8Ga18Ge28 Borures

β-FeSi2

Si0.80Ge0.20 Pb1-xSnxTe1-ySey CeFe3.5Co0.5Sb12 Zn4Sb3 Zn4 -xCdxSb3 Bi2-xSbxTe3

Thermoelectric materials: p- type ZT Temperature (K)

Mo3Sb7+Te, Ru,Fe

2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 13

New: skutterudites clathrates chalcogenides semi Heusler

• xides

200 400 600 800 1000 1200 1400 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Ti0.5(Zr0.5Hf0.5)0.5NiSn0.998Sb0.002 In0.2Ce0.2Co4Sb12 In0.2Co4Sb12 Ba8Ga16Ge30 Ba0.3Co3.95Ni0.05Sb12 SrPbO3 (Zn0.98Al0.02)O - UFP LaTe1.45 Si0.80Ge0.20

β-FeSi2

Pb1-xSnxTe1-ySey CoSb3 Bi2(Sb,Te)3 Bi2-xSbxTe3

Thermoelectric materials : n- type ZT Temperature (K)

In203+Ge

2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 14

LaB6: La Einstein oscillator in Debye solid of B Specific heat LaB6: ADP (300K) => TEinstein of La & TDebye of B

Cage compounds

Used with success in various series of materials

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 15

Possible minimum value of lattice thermal conductivity ~ λL=1/3CvvSd Cv specific heat estimated from Dulong & Petit law ( ) vs speed of sound in the material d mean free path of phonons (sometimes chosen equal to lattice parameter)

Lattice thermal conductivity, specific heat, TDebye, TEinstein

Cv = f CDebye + (1-f) CEinstein f = fraction lattice atoms (B), (1-f) fraction (La) CEinstein contribution Ln to the molar specific heat Cv CDebye contribution of lattice to Cv

( )

( )

∫

− =

T x x D B A D

D

dx e e x T k N C

/ 2 4 3

1 9

θ

θ

2 2

1 3 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ =

T T E B A E

E E

e e T k N C

θ θ

θ

( )

3 / 1 2

6 2 n h k v

B D sound

π π θ =

B A T

k N R C 3 3 = →

∞ →

effects of T

3 4

) ( 5 12 ~ :

D B A D D

T k N C T θ π θ <

B A D

k N C T 3 : → ∞ →

B A E

k N C T 3 : → ∞ → false C T

E

: → →

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 16

CoSb3 - Im3 LaFe4Sb12 - Im3 Ce-12Sb Ce-8Fe

Skutterudites

Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Co Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Co Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Co Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb

CoSb3 cage

Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb a b c Sb La Sb Sb La La La Sb Sb Sb Sb Sb Sb Sb Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb La Sb Sb Sb Sb Sb Sb Co Co Co Co Sb Sb Sb Sb Sb Sb Sb Sb La La Sb La La Sb

a b c Sb Sb Sb Sb Co Sb Sb Sb Co Sb Sb Sb Sb La Sb Sb Sb Co Sb Sb La Sb Co Sb La Sb Co Sb La Sb Sb Co Sb Sb Sb La Sb Sb Sb Sb Co Sb Sb Sb Co Sb Sb Sb Sb

a b c

Peritectic => Preparation Crystals Physical Prop. Brian Maple

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 17

Ce cage in CeFe4Sb12 d(Ce-Sb)=3.39Å Rcovalent=1/2 d(Sb-Sb)=2.92/2 d-Rcovalent = 1.93 >> Rionique (Ce) ~ 1.14Å Ce weakly bound - can rattle - strong ADP agreement Uiso from neutron TEinstein (Tl) ~52K

Chakoumakos Acta Cryst 55,341, 1999 Sales PRB 61,2475, 2000

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 18

larger cage with Sb => amplitude ADP stronger => thermal conductivity smaller

Fleurial, ICT Dresden 1997

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 19

RyM4X12, (R = rare earth (RE) or actinides (Ac) or an electropositive element; M = Fe, Co, Ni; X = Sb, Sn, Ge, Te).

BayCo4Sb12 LayCo4Sb12 CeyCo4Sb12 EuyCo4Sb12 YbyCo4Sb12 TlyCo4Sb12 ymax =0,44 ymax =0,23 ymax =0,1 ymax =0,54 ymax =0,25 ymax =0,22 Chen, JAP 90,1864, 2001 Nolas, PRB 58,164, 1998 Chen, PRB 55, 1476, 1997 Berger, ICT, Beijing, 2001 Anno, ICT, Cardiff, 2000 Sales, PRB 61, 2475, 2000 Occupation limits of A-site in AyCo4Sb12

In CeyCo4Sb12 y~0,1 BUT in CeyFe4Sb12 y ~0,9 with K, Na: y=1 (Leithe Jasper PRL 91, 037208, 2003)

Samples highest ZT T ZT (K) Ref. (CoSb3)0.6+(FeSb2)0.4 0.37 773 Katsuyama, JAP 88,3484, 2000 Co0.94Ni0.04 Sb3 0.5 750 Katsuyama, JAP 93,2758, 2003 CoSb3 0.21 600 Katsuyama, JAP 84,6708, 1998 CoSb3 + 0.75%Te 0.5 600 Wojciechowski, Freiberg, 2001 CoSb3+4%Te 0.8 750 Nagamoto, ICT,Nagoya, 1998 IrSb3 0.15 800 Slack, JAP 76,1665, 1994 Samples Type highest ZT T ZT (K) Ref. Ba0.24Co4Sb11.87 n 1.1 850 Chen, JAP 90,1864,2001 Ba0.3Co3.95Ni0.05Sb12 n 1.2 800 Dyck, JAP 91,2002

CayCo4–xNixSb12

p 1 800 Puyet, JAP 97,083712,2005 Ce0.28Co2.5Fe1.5 Sb12 p 1.1 800 Tang, JMR 16,836,2001 CexFe3.5Co0.5Sb12 p 1.4 (1.2) 870 Fleurial, ICT, Pasadena, 1996 Eu0.42Co4Sb11.37Ge0.50 n 1.1 700 Lamberton, APL 80,598,2002 In0.25Co4Sb12 n 1.2 570 He, CM18,759, 2006 In0.2Ce0.2Co4Sb12 n 1.7 570 He, USPatent 2005 LaxFe4-yCoySb12 p 1 800 Sales, Science 272,1325,1996 NdxCo4Sb12 n 0.45 700 Kuznetsov, JPCM 15,5035,2003 TlxCo4Sb12 n 0.2 300 Sales, PRB 61,2475,2000 Yb0.8Fe3.4Ni0.6Sb12 p 1 800 Anno, ICT Long Beach,2002 Yb0.19Co4Sb12 n >1 600 Nolas, MRS, Boston, 2000 (Ce,Yb)0.4Fe3CoSb12 p 1 800 Bérardan, JAP 98,033710,2005 Some highest ZT values in ternary skutterudites

>1

Some highest ZT values in binary skutterudites

Composite: YbyCo4Sb12/Yb2O3 ZT=1.3 at 850K Zhao APL 89,092121,2006 NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 20

Phenomenological model of Sales

The atom « rattler » ~ an Einstein oscillator (harmonic oscillator, localised) the rest of lattice ~ a solid of Debye (ensemble of lattice atoms vibrations) TDebye : θD estimated from

⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Φ = 4 1 6

2

T T Mk nh B

D D D B moy iso

θ θ θ

( )

∫

− = Φ

x y

dy 1 e y x 1 x B

moy iso

B mean value for Fe & Sb molar mass WITHOUT Ln Nbre atoms WITHOUT Ln

M n

TEinstein : θE estimated from

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = T mk h B

E E B R iso

2 coth

2

θ θ B

R iso

B of Ln Mass of Ln

m

50 100 150 200 250 300 350 400 450 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

θD = 245 K

Biso

moy (Å 2)

Température (K) Ce0,85Fe4Sb12 Yb0,92Fe4Sb12

θD = 260 K

50 100 150 200 250 300 350 400 450 0,0 0,5 1,0 1,5 2,0 2,5

θE = 63 K

Biso

R (Å 2)

Température (K) Ce0,85Fe4Sb12 Yb0,92Fe4Sb12

θE = 65 K

Sales JSSC 146,528, 1999 Bérardan Thesis Thiais July 2004

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 21

Clathrates

Compounds obtained by inclusions of molecules of one species in cages

• f crystalline lattice of another species.

A8GaxGe46-x[ ]y structure type I (Na8Si46 type, cubic, P m -3 n) Ga, Ge: pentagonal dodecahedron X20 et tetrakaidecahedron X24 Projection 111 Numerous structures: type I the most studied for TE

Ba G e Ge Ge Ga Ba G e Ba G e Ba Ge Ge G e Ge Ga Ba Ba Ba G e Ge Ge Ga Ga Ga G e Ge G e Ba Ge Ge Ba Ge Ba Ge Ge Ge Ga G a G a Ge G e G e Ge G e G e Ge Ge Ge Ba Ga Ga Ga G e Ge Ge Ga G a G a Ge Ge Ge Ge Ba Ba Ge Ge Ba Ge Ba Ge Ge Ge Ba Ge Ge Ba Ba Ba Ba G e G e G e G e Ge Ge Ge Ge Ge Ga Ga Ga G e Ge Ge Ga Ga Ga Ba Ba Ba Ba Ba Ba Ga Ge Ge Ge Ge Ge Ge Ge Ge Ge G a Ga Ga Ga Ga Ga Ga G a Ga G e Ge G e Ge Ge Ge Ge Ge Ge Ge Ba Ba G e Ge G e Ba Ba G e Ba Ba Ba G e G e Ba Ge G e Ba G e G e Ge Ge Ge G e Ge Ge Ge Ga Ga Ga G a Ga Ga G a G a Ga Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ga Ba Ba Ba Ga Ga Ga Ge Ge G e G e Ge Ge Ge G e Ge Ga Ga Ga Ga Ga Ga Ga Ga Ga G e Ge G e G e Ge G e G e Ge Ge Ge Ge Ge Ba Ba Ba Ge Ba Ge Ge Ba Ba Ba Ge Ba Ge Ge Ba Ba Ba Ge Ba Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge G a Ga G a Ga Ga G a G a Ga Ga Ge Ge G e Ge G e Ge G e G e Ge Ga Ga Ga Ba Ba Ba Ba Ba Ba Ba Ga Ga Ga Ge G e G e G e Ge Ge G e Ge Ge G a Ga G a Ga Ga G a Ga G a Ga Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ba Ge Ge Ba Ge Ba Ge Ba Ge Ba Ge Ba Ba Ba Ba Ge Ba Ge Ba Ba Ge Ge Ge Ge G e Ge G e Ge G e Ge G e G e Ga Ga Ga Ga Ga Ga Ga Ga Ga Ge G e Ge Ge Ge G e G e Ge Ge Ga Ga Ga Ba Ba Ba Ga Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge Ge G a Ga G a Ga Ga Ga Ga G a Ga Ge Ge Ge Ge Ge Ge G e G e G e Ba Ba G e G e Ba Ba Ba Ge Ba G e Ba G e Ba Ge Ge G e G e Ba Ge Ge Ge G e G e Ge Ge Ge Ge Ga Ga Ga Ga G a Ga Ga G a Ga Ge Ge Ge Ge Ge Ge Ge Ge Ge Ga Ba Ba Ba Ba Ba Ba Ga Ga Ga G e Ge Ge Ga Ga Ga G e Ge Ge Ge G e Ge G e Ge G e Ba Ge Ge Ba Ge Ba Ba Ge Ba Ge Ba Ge Ba Ge Ge Ba Ge Ba Ge Ge Ge G a G a Ga Ge Ge G e Ga Ga Ga Ba Ge G e G e Ge Ge G e G e Ge Ge Ga G a G a Ge Ge Ge Ba Ge Ge Ge Ba Ba G e Ge G e Ga Ga Ga G e Ge Ge Ba Ba Ba Ga G e Ge Ge G e Ge G e Ba Ba Ba Ga Ge G e Ge Ba

All properties Peter Rogl

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 22

A8GaxGe46-x[ ]y structure type I (Na8Si46 type, cubic, P m -3 n) In the X24 cages, atoms A have very strong ADP => very weak λL (~1 W.m-1.K-1 ~ SiO2) Sr8Ga16Ge30: ellipsoïds around Sr(2) & Uiso at center of X24 cage

Ba larger cage X24, Eu smaller cage Cu Si atoms Eu2Ba6Cu4Si42

Nolas APL73,178, 1998 Chakoumatos 2002 Mudryk JPCM 14,7991, 2002

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 23

Intermetallic clathrates MGe20

+ cage Ge28 Clathrate II NaxSi136 Clathrate V Clathrate VIII Ba8Ga16Sn30 distortion + cage Ge24 Clathrate I K8Ge46 2Ge -> Ba Clathrate IX Ba6Ge25 partial substitution Ge Clathrate IX Ba6Ge21In4 Cordier' phases Ba8Ni6Ge40 by metal d / site 6d hazard phases 8-16-30, 8-12-33, 8-8-36 mixtes phases (Eu) + polyhedron Clathrate III Cs30Na~3Sn~162 Clathrate IV K7Ge~38 + defects, distortions Superstructures / distorded Ba8Cu16P30 - Sn14In10P13I8 # clathrates Ba15Na204Sn310

Mudryk 2002, Rogl ICT 2003, Hvar 2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 24 1811 Davy H. clathrate "Cl2 10.H2O" 1965 Kaspar J. 1st intermetallic clathrate Na8Si46, NaxSi136 1973 Menke H. 1st ternary clathrate X8A8Ge38 (X=Br, Cl, I; X=P, As, Sb) 1986 Eisenmann B. 1st clathrate type VIII: Ba8Ga16Sn30 1988 Kroener R. chiral clathrate Ba6In4Ge21 (type IX) 1998 Nolas G. TE properties of Sr8Ga16Ge30 2000 Fukuoka H. 1st binary type IX clathrate 2000 Sung-Jin Kim clathrates of Sn &In (TE) Ba6Ge25?x, Ba6Ge23Sn2, & Ba6Ge22In3 2001 Chakoumakos B.C. magnetism in Eu8Ba16Ge30 2001 Latturner S. clathrates of Rb : Rb8Na16Si136 2001 Myles C.W. clathrates of Cs (TE) : Cs8Sn46- Cs8Sn44[ ]2- Cs8Ga8Sn38- Cs8Zn4Sn42 2002 Kitagawa J. fluctuating valence (TE) in ~ clathrate Eu3Pd20Ge6 2002 Mollnitz L. clathrates of K (TE) : K8Sn25- K8Sn46- K8Sn44+[ ]Sn 2002 Nolas G.S. type II clathrates of Si, Ge (TE) : R8Na16X136 (R=Cs, Rb) (X=Si, Ge) 2003 Mudryk Ya. clathrates of substituted Eu (TE) Eu2-x(Sr,Ba)6-xMySi46-y (M=Al, Ga) 2003 Petkov V. disorder of Ba in Ba6Ge25 2004 Yang C.K. clathrates of Mn (TE) : Ba8Mn2Ge44 - Ba8 Mn4Ge42 2006 Kishimoto K. Iodine clathrate (TE) Ge38Sb8I8 & Sn38Sb8I8 2006 Guloy A.M. Clathrates WITHOUT insertion : [ ]24Ge136 2006 Srinath Magnetocaloric effects in Eu8Ga16Ge30 2007 Kishimoto K. clathrate de tellure (TE) Te8Si46-xPx 2007 Zaikina J.V. Iodine substituted clathrates (TE): I8-xBrxSn24P19.3(2) (x <8) - I8-yClySn24P19.3.(2) (y <0.8) 2007 Deng S. clathrates of Zn (TE): Ba8Ga16ZnxGe30-x 2008 Alleno E. Ge vacancies in Zn- clathrates (TE) : Ba8ZnxGe46-x-z[ ]y

Some clathrates … & TE properties … Best TE: ZT~1.4 n-type Ba8Ga16Ge30 - ZT~1 p-type Ba8Ga18Ge28 Hvar 2005 <= sorry for >50

• thers

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 26

Penta-tellurides Tl2MTe5 (M=Sn, Ge)

Tl2MTe5 (M=Sn, Ge) derived Re3Te5 Tl2SnTe5 : 2 sites of Tl - strong ADP on Tl(1)

• ZT~0,6 at 300K - solid solutions non investigated.
• problem of environment(Te, Tl)
• good values of ZT only in p-type.
• problem of environment (Te)
• weak ZT in both types p & n.

& Re3Te5.

Tl(1) Tl(2)

Sharp APL 74, 3794, 1999 NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 27

Tl-tellurides TlAg9Te5 - Tl9BiTe6

• complexes structures & weak thermal conductivity
• High ZT BUT problem of environment (Te, Tl)
• special properties of Tl ? Very weak bonding of Tl & weak elastic modulus

penta tellurure TlAg9Te5 Tl9BiTe6 disordered variant of Tl5Te3

Kurosaki APL 87, 061919, 2005

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 28

Chevrel' phases : Mo6X8 (X=S, Se, Te)

A tri-dimensional network of pseudo-cubic clusters Mo6X8 (X=S, Se, Te) these clusters form cavities or channels => weak thermal conductivity can be intercalated by various elements from metallic state in Mo6X8 to semi-conducting state

ZT of 0,6 at 1150K found in Cu3,1Mo6Se8 in the series MxMo6Se8 (M= Cu, Cu/Fe, Ti)

Caillat JPCS 59,1139,1998 Roche JPCM 10,333, 2000 Structure of Re6Te15 (cluster [Re6] surrounded by 8 Te & O cage can be inserted)

Mo X M

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 29

Phases with clusters Mo9X11 Mo - X

Projection 100

Ag3.6Mo9Se11 ( Ag)

structures with tunnel insertion atoms (Ag, Cs, Cl,) in the cages => semiconductor / semimetal

• α = 72 µV.K-1 @ Tamb in Ag3.6Mo9Se11

with ρ = 3-4 mΩ.cm

• M. Potel, P. Gougeon, O. Merdrignac-Conanec, M. Lecroc, M. Guilloux-Viry

Meeting French TE GDR July 2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 30

Phases with vacancies

already in skutterudites, clathrates

Heusler ZrNi2Sn Half Heusler ZrNiSn

Half Heusler 3 sub-lattices with 18 valence e-: semiconductor possibility doping on 3 sub-lattices => diffusion of phonons by mass fluctuations (substit. + vacancies)

200 300 400 500 600 700 800 0.00 0.25 0.50 0.75 1.00 1.25 1.50

(Zr0.5Hf0.5)NiSn Ti0.5(Zr0.5Hf0.5)0.5NiSn1-ySby y=0 Ti0.5(Zr0.5Hf0.5)0.5NiSn1-ySby y=0.002 Ti0.5(Zr0.5Hf0.5)0.5NiSn1-ySby y=0.006

Semi Heusler thermoélectriques de type n ZT Température (K)

from TiNiSn (ZT<0,4 at 750K) & ZrNiSn Hf0.5Zr0.5Ni0.8Pd0.2Sn0.99Sb0.01 n-type, maximum of ZT at 800K of 0,7 Ti0.5(Zr0.5Hf0.5) 0.5NiSn0.98Sb0.02 n-type ZT>1,4 à 700K.

Zr Ni Sn

Shutoh ICT 2003 - JAC 389,204, 2005

LnPd(Sb,Bi) Kaczorowski

VFeSb VCoSb + Ti, Mn, Zr Good S - low ZT Jodin: ICT2001, Thesis 2002, PRB 70, 2004

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 31 50 100 150 200 250 300 350 400 450 500 100 200 300 400 NbIrSn S (µV/K) T (K)

(Nb1-xHfx) Co(Sn1-ySby) - NbCo(Sn1-ySby) studied - NbCoSn + Ti, Fe, Sb No substitution tried, (to my knowledge), from this family Nb-Ir-Sn Kawaharada, JAC 377,312, 2004- 384,303,2004 Ono ICT Adelaide,2004

Solid solutions LnPdSb - LnPdBi possible ?

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 32

~ 1960, Ioffe Institut shows that compounds Mg2X (X=Si, Ge, Sn) are semiconductors & bands structure may favor thermoelectric properties. Various types of substitution (Si, Ge, Sn, Al, Ca, Sb …) have been tested, the best result with the largest mass difference contribute to decrease the thermal conductivity, i.e. with Si-Sn. Best ZT ~1.1 n-type was obtained in 2006 in the same Institute

Effects of substitutions

Mg2Si1-xSnx

200 400 600 800 1000 1200 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Mg2Si0.6Sn0.4 Mg2Si0.4Sn0.6 n-(Si,Ge) ZT T (K)

Fedorov ICT2003 ICT 2006 - ECT2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 33

Zn4Sb3 & derivatives

Structure 78: shortest bondings Zn-Sb & Zn-(Zn,Sb) Zn Sb (Zn,Sb)

a b c Sb1 Sb2 Sb1 Sb2 Sb1 Zn Zn Zn Sb2 Zn Zn Zn Sb2 Zn Zn Zn Sb1 Sb2 Sb1 Sb1 Sb2 Sb1 Sb1 Sb2 Sb1 Zn Zn Zn Sb2 Zn Zn Zn Sb2 Zn Zn Zn Sb1 Sb2 Sb1 Sb2 Sb1 Sb1 Sb2 Sb1 Sb2 Sb1 Zn Zn Zn Sb2 Zn Zn Zn Sb2 Zn Zn Zn Sb1 Sb2 Sb1 Sb1 Sb2 Sb1 Sb1 Sb2 Sb1 Zn Zn Zn Sb2 Zn Zn Zn Sb2 Zn Zn Zn Sb1 Sb2 Sb1 Sb2 Sb1

Structure 71: shortest bondings Zn-Sb1 & Zn,Sb2 Zn36Sb30 ~ Zn4Sb3,3 Zn Sb1 Sb2

Complex structures

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 34

β phase leads to materials with strong p- type ZT with maxima of 1.25 at ~650K in β- Zn4Sb3 Can be increased by substitution to ZT=1.4 at lower temperature ~525K in Zn3,2Cd0,8Sb3. Vacancies and intersticials on the Zn site & 2 types of Sb atoms (spherical ions Sb3- & dimers Sb4-) an important disorder (in fact the composition is ~ Zn6-δSb5) the thermal conductivity decreases.

Caillat 1997, 1999 Schweika PRL 99,125501, 2007

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 35

Disorder effects already seen : Zn4Sb3

Yb14MnSb11

Tetragonal structure Yb14MnSb11 I41/acd complex Made of various structural units ZT > 1 (~1200K) with p- type. flexibility to accommodate various elements (ZT ?)

a b c Mn Sb1 Mn Mn Sb1 Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb3 Sb3 Sb3 Sb3 Yb3 Yb3 Yb3 Yb3 Yb2 Yb2 Yb2 Yb2 Yb3 Yb3 Yb3 Yb3 Sb4 Sb4 Sb4 Sb4 Sb2 Sb2 Sb2 Sb2 Sb2 Sb3 Sb3 Sb3 Sb3 Yb1 Yb1 Yb4 Yb4 Yb4 Yb4 Yb2 Yb2 Yb2 Yb2 Yb4 Yb4 Yb4 Yb4 Sb4 Sb4 Sb4 Sb4 Yb1 Yb1 Yb1 Yb1 Sb4 Sb4 Sb4 Sb4 Yb4 Yb4 Yb4 Yb4 Yb2 Yb2 Yb2 Yb2 Yb4 Yb4 Yb4 Yb4 Yb1 Yb1 Sb3 Sb3 Sb3 Sb3 Sb2 Sb2 Sb2 Sb2 Sb2 Sb4 Sb4 Sb4 Sb4 Yb3 Yb3 Yb3 Yb3 Yb2 Yb2 Yb2 Yb2 Yb3 Yb3 Yb3 Yb3 Sb3 Sb3 Sb3 Sb3 Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Mn Sb1 Sb3 Sb3 Sb3 Sb3 Yb3 Yb3 Yb3 Yb3 Yb2 Yb2 Yb2 Yb2 Yb3 Yb3 Yb3 Yb3 Sb4 Sb4 Sb4 Sb4 Sb2 Sb2 Sb2 Sb2 Sb2 Sb3 Sb3 Sb3 Sb3 Yb1 Yb1 Yb4 Yb4 Yb4 Yb4 Yb2 Yb2 Yb2 Yb2 Yb4 Yb4 Yb4 Yb4 Sb4 Sb4 Sb4 Sb4 Yb1 Yb1 Yb1 Yb1 Sb4 Sb4 Sb4 Sb4 Yb4 Yb4 Yb4 Yb4 Yb2 Yb2 Yb2 Yb2 Yb4 Yb4 Yb4 Yb4 Yb1 Yb1 Sb3 Sb3 Sb3 Sb3 Sb2 Sb2 Sb2 Sb2 Sb2 Sb4 Sb4 Sb4 Sb4 Yb3 Yb3 Yb3 Yb3 Yb2 Yb2 Yb2 Yb2 Yb3 Yb3 Yb3 Yb3 Sb3 Sb3 Sb3 Sb3 Mn Mn Sb1 Mn Sb1 Sb1 Sb1 Mn Mn Sb1 Mn Sb1 Mn Sb1 Mn

Yb Mn Sb bonding Sb-Sb bonding Mn-Sb

Brown Chem Mat 18,1873, 2006

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 36

Antimoniures complexes

Mo3Sb7-XTex (x=1,5 et 1,6) exists when 51 < VEC <56 semiconductor 55 Substitution Ru, Fe, Te: * Mo3Sb7-xTex x=1.6 and 1.5 ZT=0.8 at 1050K * Mo3-y-zRuyFezSb7 ZT=0.8 at 1000K with (y,z)= (0.16,0.5) et (0.1,0.7) better than (Si,Ge) - p-type

Ir3Ge7 (Im3m) Infinite Chaînes

Structure: clusters Mo6 "LaB6"

Sb2

Mo3(Sb1)4(Sb2)3 40 atoms per unit cell

Gascoin JAC427,324, 2007- Candolfi, thesis Oct. 2008

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 37

β- K2Bi8Se13

K2Bi8Se13 forms two phases : α-K2Bi8Se13 (triclinic, gr. P-1d) β- K2Bi8Se13 (monoclinic, gr. P 21/m). β- phase : fragments of Bi2Te3, CdI2 & NaCl + mixte occupancy of sites by S/Se.

K2Bi8Se9S4 : (projection 010)

complexe structure, alcalin atoms rattling in the tunnels very low thermal conductivity K2Bi8-xSbxSe13 dopings increase S (p-& n-type )

ZT insufficient (cooling applications)

a b c Bi21 K1 Se11 Bi91 Se3 Bi7 Bi9 Bi5 Bi22 Se10 Bi22 S4 Se5 Se8 Se2 Bi91 K3 Bi81 Se12 Bi2 Bi8 Bi21 Bi21 Bi4 Se11 Bi6 Se1 Bi9 Se3 Bi5 Se6 Se7 Bi3 Se13 Bi1 K1 Se2 Se1 Bi6 Bi5 Bi22 Bi91 K1 Bi7 Se11 Se3 Bi81 K3 Bi8 Se12 Bi9 Se5 Se10 Se8 S4 S9 Bi2 Se13 Se1 Se3 Se11 Bi9 Bi91 Bi21 Bi22 K1 Bi5 Se1 S9 Bi3 Se13 Bi1 Se6 Se7 K3 Bi8 Bi81 Bi2 Bi4 Se12 Se10 Se8 Bi3 S4 Bi6 Se1 S9 Se5 Se7 Se6 Se2 Bi5 Bi7 Bi1 Bi3 S9 Se3 Bi9 K1 Bi91 Bi2 Bi4 Se11 Bi1 Se8 Bi21 Se13 Se7 Se6 Bi4 Se5 Se10 Bi81 Bi8 Bi22 S4 Se12 Bi3 K3 Bi6 S9 Bi7 Se2 Se7 Bi1 Se6 Bi4 Bi22 Bi21 K1 Se11 Se3 Bi91 Bi9 Bi7 Bi5 Se2 Se1 S4 Se5 Bi6 Bi21 Se10 Se12 Se8 Bi8 Bi9 Bi22 K3 Bi4 Bi2 Bi81 Se6 Se7 Bi22 Bi21 Se11 K1 Bi91 Se3 Bi9 Se13 Bi1 Bi6 Bi5 Se2 Bi7 Se3 Se11 Bi91 K1 Se12 Se1 Bi5 S9 S4 Bi3 Se5 Se1 Bi8 K3 Bi81 Se8 Se10 Se13 Bi22 Bi2 Bi21 Bi91 K1 Se3 Se11 Bi9 Bi5 Se1

K Bi Se S

Kyratsi JAP100,123704 2006 Ghelani MRS 626, 2000

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 38

Cobaltites

Na1 Na2

Hexagonal layered structure Na0.75CoO2 Mixte Valence Co 3.25 2 Na- sites partially occupied (Na1 ~ 0.25, Na2 ~ 0.5)

Masset PRB 62,166,2000

Ca3Co4O9

Hébert PRB64,1721012001

TlSr2Co2Oy

Maignan JPCM15,2711,2003

Bi2-xPbxSr2Co2Oy

NaCo2O4: Metallic oxide

Terasaki PRB56,12685, 1997

"misfit" oxides [AO)n]RS[CoO2]b1/b2

Ca3Co4O9 (b~ 8b1 ~13b2) best ZT in such (PXal) oxides ~ 0.4 at 1000K in n- & p- types p-type: ZT=0.56 NaxCoO2 - n-type: ZT=0.33 In2O3-ZnO

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 39

In2-xGexO3

~ vacancy fluorine CaF2 Fm3m - In2O3 Ia-3 disordered planes 0.5 atom %: solubility limit of Ge in In2O3 In2-xGexO3 : In2O3 + inclusions In2Ge2O7 decrease λ Micro-COMPOSITE In1.8Ge0.2O3 (n): ZT > 0.45 à 1243K

Bérardan SSC146,97,2008

Composite

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 40

Ag1-xPb18SbTe20 ZT = 2.1 à 800K

(nanophases of AgPb3SbTe5 in PbTe) Nanocomposites - Experiment (false bulk ~ 2004) real nanocomposites ~ 2005-6

Lin H - PRB,72, 174113 (2005) NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 41

NANO EFFET NANO EFFET IN TE IN TE

3D: S, σ, λ related => difficulties to adjust the 3 Particules sizes ~ q.q. nm ~ unit cell ~ mean free path => changes changes in DOS => S increase of interfaces diffusion => λ expected increase for ZT low Dim: S, σ, λ independently adjustable

Hicks L.D., Dresselhaus M.S. - PRB,47, 16631 (1993), PRB,47, 12727 (1993)

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 42 Dresselhaus M.S. - Adv Mat 19,1043 (2007) NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 43

NANO NANO IN TE IN TE

Theory (~1993) Experiments (~ 1996) Nanocomposites - Experiment (false bulk ~2004) real nanocomposites ~ 2005-6 1D, 2D materials Problem of large quantities Prediction : smaller dimensionality higher ZT

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 44 NAN NANO COMP MPOSITES Preparation: nano powder in matrix (decrease λ) much less expansive (/ 2D or 1D) Shaping: AVOID GRAIN GROWTH & reaction (Spark Plasma Sintering) Stability: thermal cycling Hydrothermal Prep. nanoBi2Te3 90%Bi2Te3+10%nanoBi2Te3 + SPS ≠ in skutterudite at 800K nano grains Yb2O3 in YbxCo4Sb12 ≠ size (quantity ?) STRONG effect on λ less on σ ZT Ni H.L., Zhao X.B., Zhu T.J., Ji X.H., Tu J.P.- JAC,397, 317 (2005) Zhao X.Y., Shi X., Chen L.D., Zhang W.Q., Bai S.Q., Pei Y.Z., Li X.Y. APL,89, 092121 (2006) Zhao L.D., Zhang B.P., Li J.F., Zhou M., Liu W.S. , Liu J. JAC under press (2007) also C60 in skutterudite decreases thermal conductivity Increases ZT Shi, ICT Long Beach 2002 APL 84,2301,2004 NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 45

SPS-1

CNRS Thiais- 50kN - 1500 Amp.- 0-2000°C (5 mn)- Vacuum- Argon

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 46

SPS-2

Ce(B,C) 50MPa 1800°C Graphite die 18 <=> thermocouple/ pyrometer

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 47

SPS-3

Time can be < 1 hour ~no grain growth Density >95%

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 48

SPS-4

Copper/Brass/Al Mm(Fe, Ni)4Sb12 50MPa- 500°C- Φ 8mm Ce(Fe, Co)4Sb12 50MPa- 470°C- Φ 15mm From ~20 nm to ~50nm "Bi2Te3 "- 50MPa- 360°C- Φ 8mm- 5min. (for CEA) Ag contacts on the surface of TE oxides (for CRISMAT)

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 49

SPS-5

Grain growth

Experimental and Rietveld-refined X-ray diffraction patterns

• f mechanically alloyed CeFe4Sb12

(top panel) and Ce0.1Fe0.1Co3.9Sb12 (bottom panel). The two insets display a comparison between the patterns of MA-CeFe4Sb12 (circle) and PM-CeFe4Sb12 (triangle) in the small and high angle region.

2000 4000 6000 20 40 60 80 100 120 1000 2000 3000

30 32 86 88 90 92 94 96

Intensity (arb. unit) CeFe4Sb12 2θ (°) Intensity (arb. unit) Measured Calculated Difference Ce0.1Fe0.1Co3.9Sb12

2θ (°) MA PM 2θ (°)

SEM image of CeFe4Sb12. Magnification 60000. DTA measurement (first heating) in MA-CeFe3CoSb12

200 400 600 800 1000 1200 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Heat flow (µV/mg) Temperature (°C) 630°C 750°C 350°C MA-CeFe3CoSb12

• D. Bérardan, E. Alleno, C. Godart,
• H. Benyakoub, H. Flandorfer, O. Rouleau, E. Leroy

ICT 2006- Vienna

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 50

Importance of electrical contacts : stable (T), non reactive, very low R

Godart C.; Alleno E.; Tena-Zaera R., APNFM 2008 - Dresden

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 51

Perspectives

STILL NEW GOOD SYSTEMS every year New bulk families: * Semiconductor

• r metal (with MIT)

* Complex structures * Possibility of cages New composites: * micro composites * nano composites

NATO ARW workshop Thermoelectrics- Hvar Sept. 2008- C. Godart 52

Thanks for your attention

T