Introduction to Thermoelectric Materials and Devices

Transcription

1 Introduction to Thermoelectric Materials and Devices 11th Semester of , Thursday Department of Energy Science Sungkyunkwan University Radioisotope Thermoelectric Generator (PbTe) Space probe to the Jupiter From JPL, NASA

2 Plan 1 Thermoelectric Phenomena and Conversion Efficiency 2 Thermoelectric Transport Theory I : Electrical Properties 3 Thermoelectric Transport Theory II : Thermal Properties 4 Measurement of Thermoelectric Properties 5 Materials Preparation : Bulk 6 Materials Preparation : Thin Film 7 Thermoelectric System : Current and Future of Module 8 Applications : Power Generation and Heat Cooling 9 Thermoelectric Materials : State-of-the-art 10 Thermoelectric Materials : Intermetallics 11 Thermoelectric Materials : Oxides 12 Thermoelectric Materials : Phonon Glass and Electron Crystal (PGEC) Materials 13 Theory and Modeling in Nanostructured Thermoelectrics 14 High efficiency in Low Dimensional Materials 15 Hybrid Energy Conversion Systems of Thermoelectrics 16 Final Exam

3 Thermoelectric Materials 1950 Bi-Te, Bi-Se, Sb-Te ZT= Pb-Te, Ge-Si, 3d Silicide ZT= PGEC, Intermetallics, Oxide ZT=1 Thin Film (Superlattice), Nanowire ZT=2 Complex Structure Nanostructure Imbedded Bulk

4 Why Oxide? : Clark Number O 99% of Earth s outer crust SiO 2, Al 2 O 3, FeO X, CaO, MgO etc 90%

5 Thermoelectric Materials : Oxide 1950 Bi-Te, Bi-Se, Bi-Sb ZT= Pb-Te, Ge-Si, 3d Silicide 1990 PGEC, Intermetallics, Oxide Oxide TE material with large ZT is preferable! Stable at high temperature cf. Intermetallic alloys, PbTe easily decompose at high temperature. Low toxicity cf. Toxic heavy metal, Bi, Sb, Te and Hg etc. Na-Co-O System ZT=2 Thin Film (Superlattice), Nanowire Complex Structure Nanostructure Imbedded Bulk Na x CoO 2 ZT > 800 K JJAP, 2001 Composition was totally CHANGED! (High Stability???)

6 Oxide Thermoelectrics Na-Co-O System High Seebeck and High Electrical conductivity Na-Co-O Single Crystal, ZT >1 at 900K. Low Thermal conductivity at high Temp. Terasaki et al. PRB, 1997 Fujita et al. JJAP, 2001 Sugiura et al. APL, 2006

7 Thermoelectric Materials : Oxide

8 Thermoelectric Materials : Oxide Na-Co-O polycrystalline, ZT >1 at 900K. High Seebeck in spite of metallic properties. BUT, No Meaning!!! Sugiura et al. APL, 2006

9 Thermoelectric Materials : Oxide Sr-Ti-O single crystal, ZT = 0.3 at 1000K. High Seebeck coefficient, high thermal conductivity. VERY DIFFICULT

10 Oxide Thermoelectrics

11 Oxide Thermoelectrics

12 Oxide Thermoelectrics SrTi 1 x Nb x O 3

13 Oxide Thermoelectrics STO BTO CTO

14 Oxide Thermoelectrics

15 Structural Diversity of Oxides Si, Ge Semiconductors Diamond Structure CaO 12CaO 7Al 2 O 3 Zeolite, LTA Apatite Na 12 (Al 12 Si 12 O 48 ) 27H 2 O Ca 10 (PO 4 ) 6 (OH) 2 NaCoO 2 InGaO 3 (ZnO) 5

16 Oxide Thermoelectrics Natural Superlattice

17 Oxide Thermoelectrics

18 Oxide Thermoelectrics

19 Oxide Thermoelectrics

20 Oxide Thermoelectrics

21 Nanostructured Oxide for Thermoelectrics Oxide TE material with large ZT is preferable! Stable at high temperature cf. Intermetallic alloys, : PbTe easily decompose at high temperature. Low toxicity cf. Toxic heavy metal : Bi, Sb, Te and Hg etc. Light Metal Oxide Electrical Insulating Property High Thermal Conductivity 12CaO 7Al 2 O 3 e doping 3-dimensionally connected Nanocage Structure S. W. Kim et al. PRB 2009, Editor Suggested Paper

22 Nanostructured Oxide for Thermoelectrics Thermal Conductivity Thermoelectric Performance CaO : ~ 15 W/mK, Al 2 O 3 : ~ 30 W/mK Amorphous-like thermal conduction Phonon Mean Free Path : 0.7 nm Modification of lattice framework with heavy mass elements and encaged species S. W. Kim et al. PRB 2009, Editor Suggested Paper

23 Thermoelectric Properties of C12A7:e C12A7:O 2 + Ti C12A7:e + TiO X Treatment Temperature, o C Time, hr

24 Thermoelectric Properties of C12A7:e S decreases with N e T 1/2 dependence : Variable range hopping Sign change with N e : Impurity-band-conduction like Si

25 Electronic Structure of C12A7:e DOS of FVB is mainly formed by the O atoms of lattice framework cages DOS of FCB and CCB is mainly formed by the component of Ca atoms The DOS at E F decreases with N e m* of C12A7 electride Semiconducting : m 0 Metallic : 0.8m 0 m* of SrTiO 3 Nb-doped STO : m 0

26 Thermoelectric Properties of C12A7:e Thermal Conductivity Acoustic Properties CaO : ~ 15 mw/k, Al 2 O 3 : ~ 30 mw/k Amorphous-like thermal conduction Varshni s equation Phonon Mean Free Path : 0.7 nm

27 Thermal Conduction in Amorphous T 3 T 2

28 Amorphous-like Thermal Conduction in Crystals

29 Amorphous-like Thermal Conduction in Crystals : Ionic Materials

30 Thermoelectric Materials 1950 Bi-Te, Bi-Se, Sb-Te ZT= Pb-Te, Ge-Si, 3d Silicide ZT= PGEC, Intermetallics, Oxide ZT=1 Thin Film (Superlattice), Nanowire ZT=2 Complex Structure Nanostructure Imbedded Bulk

31 Thermoelectric Materials : Current Status 1950 Bi-Te, Bi-Se, Bi-Sb ZT= Pb-Te, Ge-Si, 3d Silicide 1990 PGEC, Intermetallics, Oxide PGEC : Phonon Glass and Electron Crystal Low Lattice Thermal Conductivity Low Electrical Resistivity Phonon Scattering by G. A. Slack High ZT High Carrier Mobility 2000 ZT=2 Thin Film (Superlattice), Nanowire Skutterudite ( CoSb 3, IrSb 3 ) 2010 Complex Structure Nanostructure Imbedded Bulk Clathrates ( Br 8 Ga 16 Si 30 ) Half-Heusler ( TiNiSn, TiCoSn, TiCoSb )

32 Thermal Conductivity (W/mK) Thermoelectric Materials : Current Status Bi-Te, Bi-Se, Bi-Sb ZT=1 Pb-Te, Ge-Si, 3d Silicide PGEC, Intermetallics, Oxide ZT=2 Thin Film (Superlattice), Nanowire PGEC : Phonon Glass and Electron Crystal Skutterudite ( CoSb 3, IrSb 3 ) Co, Ir Sb square 12 IrSb 3 La Ir 4 Ge 0.3 Sb 11.7 La 0.3 Ir 4 Ge 0.9 Sb 11.1 La 1 Ir 4 Ge 3 Sb Temperature (K) Filled Skutterudite : ZT>1 at 1000K, Low Thermal Conductivity Rattling Effect 2010 Complex Structure Nanostructure Imbedded Bulk Clathrate A 8 B 16 C 30 A= Na, Ba, Sr, Eu, etc B = Al, Ga C= Si, Ge, Sn ZT=1 at 1000K Cage

33 Thermoelectric Materials : Current Status Bi-Te, Bi-Se, Bi-Sb ZT=1 Pb-Te, Ge-Si, 3d Silicide PGEC, Intermetallics, Oxide ZT=2 Thin Film (Superlattice), Nanowire Ti PGEC : Phonon Glass and Electron Crystal Half-Heusler ( TiNiSn, TiCoSn, TiCoSb ) Ni Sn Figure of merit, ZT TiNiSn X = 0 X = 0.05 X = 0.2 Ti 1-X Hf X NiSn 0.99 Sb Temperature (K) 2010 Complex Structure Nanostructure Imbedded Bulk

34 Zn4Sb3

35 Zn4Sb3

36 CsBi4Te6

37 CsBi4Te6

38 Yb14MnSb11

39 Yb14MnSb11

40 Yb14MnSb11

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