Nano Structured Composite Materials for Thermoelectric Applications - PowerPoint PPT Presentation

Nano Structured Composite Materials for Thermoelectric Applications Sung Jin Kim Sung-Jin Kim Ewha Womans University Department of Chemistry and Nano Science Department of Chemistry and Nano Science April 5, 2010

Thermoelectricity 연구분야 온도차에 의해 기전력이 발생하는 현상(Seebeck 효과) 또는 전류에 의해 열이 흡수,발생이 생기는 현상 (Peltier효과) 응용분야 응용분야 열전냉각 (Thermoelectric cooling) 열전발전 (Power generation) NAS NAS A 2 www.spaceref.com/news/viewpr.html?pid=18796

Configuration of Thermoelectric Module Configuration of Thermoelectric Module HEAT IN therm oelem ent electrical conductor conductor electrical insulator n p n n n p p p − + + HEAT OUT Laser Cooling Modules

Thermoelectric Figure of Merit Z= α 2 σ / κ • Seebeck coeff. ( α ) : morphology, doping state • Electrical conductivity( σ ) : carrier concentration El t i l d ti it ( ) i t ti • Thermal conductivity ( κ ) : phonon scattering

Optimum Transport Coefficients Figure of Merit : ZT S σ 2 S T = ZT κ = κ e + κ ph κ = κ + κ k k κ el - High Seebeck coefficient tot el - High electrical conductivity Hi h l t i l d ti it κ t K K K K K K - Low thermal conductivity κ latt L L L L L L Difficulties in increasing ZT in bulk ators m aterials : tals T ZT Met I nsul S ↑ ↔ σ ↓ Sem iconductor σ ↑ ↔ S ↓ and k ↑ ↑ ↓ ↑ 17 17 17 17 17 17 18 18 18 18 18 18 19 19 19 19 19 19 20 20 20 20 20 20 21 21 21 21 21 21 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 Carrier Concentration 5

Selection Criteria for Candidate Materials m = effective mass m m τ τ τ = scattering time 3/2 x y y T T r = scattering parameter m + ∝ γ ( 1/2) r z k latt = lattice thermal Z e max k conductivity latt T = temperature T = temperature γ = band degeneracy Guiding Principles: Guiding Principles: � Narrow band-gap semiconductors : Single carrier systems � Heavy elements : High μ , low κ � Large unit cell, complex structure : low κ � Highly anisotropic or highly symmetric � Highly anisotropic or highly symmetric � Complex compositions : low κ , complex electronic structure � Mass Fluctuation : low κ � High density of states near the Fermi level : high Seebeck � Hi h d it f t t th F i l l hi h S b k coefficient Science, 303, 818

New direction : Nano-based Thermoelectrics • Minim izing the therm al conductivity : Therm al conductivity can be significantly reduced by the scattering of conductivity can be significantly reduced by the scattering of unw anted heat flow at the interfaces I nterfaces that Phonons Electrons Scatter Scatter Phonons but not Electrons Λ = 10-100 nm Λ = 1-10 nm Mean Free Path λ = 10-50 nm λ = 1 nm Wavelength • Maxim izing Seebeck coefficient: Electronic properties m ay be dram atically m odified due to the electron confinem ent in nanostructures w hich exhibit low - confinem ent in nanostructures w hich exhibit low dim ensional behaviors.

New Classes of Promising Thermoelectric Materials Nature 4 1 3 , 5 9 7 ( 2 0 0 1 ) Science 2 9 7 , 2 2 2 9 ( 2 0 0 2 ) Science 3 0 3 , 8 1 8 ( 2 0 0 4 ) Ag-Sb– rich PbSeTe/ PbTe QD Majum dar, Science 3 0 3 , 7 7 7 ( 2 0 0 4 ) AgPb 1 8 SbTe 2 0 ZT = 2 .2 @ Super-lattices Super lattices 8 0 0 K 8 0 0 K 3.5 Science 3 2 1 , 5 5 4 ( 2 0 0 8 ) 3.0 2.5 0K (ZT) 300 Nano m aterials N t i l 2.0 1.5 1.0 Bulk m aterials Bulk m aterials 0.5 Tl 0 .0 2 Pb 0 .9 8 Te ZT = 1 .5 @ 7 7 3 K 0.0 1950 1960 1970 1980 1990 2010 1950 1960 2000 Year Science 3 2 0 , 6 3 4 ( 2 0 0 8 ) Nature 4 5 1 1 6 8 ( 2 0 0 8 ) Nature 4 5 1 , 1 6 8 ( 2 0 0 8 ) Nature 4 5 9 ( 2 0 0 9 ) Sb– rich Bi x Sb 2 -x Te 3 I n 4 Se 3 ZT = 1 .5 @ 7 0 0 K Nanocom posite

Theoretical studies Nanodot Nanocom posites Nanograined Nanocom posites 2.5 2.5 1.8 1.8 1.8 1.8 Λ = 1-10 nm < L 1 10 L 1.5 Electron m ean free path Woochul Kim, Yunsei Univ.

New Approach Nanoparticles Embedded in Bulk Thermoelectric Materials Phonon Electron nanorod + Coherent interface (Matrix/nanoparticl es) nanoparticles nanoparticles Matrix Matrix + nanorod, nanoparticles Type of Bull Nanoparticles Nanorods Matrixes Bi 2 Te 3 Bi 2 Te 3 PbTe Bi 2 Se 3 Bi 2 Te 3 Bi 2 Te 3 Sb 2 Te 3 CdSe In 2 Te 3 Bi x Sb 2 x Te 3 Te 2 3 x 2-x 3 Bi

Synthesis of Various Nanoparticles � Size Control Bi( C 2 H 3 O 2 ) 3 1 -Dodecanthiol ( or Sb( C 2 H 3 O 2 ) 3 ) 75 o C 80 o C Oleylam ine, 1 -Octadecene + + Various reaction temperature Te-TOP ( or Se-TOP) 85 o C 90 o C Various Source � M � Morphology Control h l C t l Bi 2 Se 3 1 4 0 o C � Composition Control 1 0 0 o C Bi 0 9(3) Sb 0 9(2) Te 3 0.9(3) Sb 0.9(2) e 3 Bi 1 9(3) Sb 0 1(1) Te 3 Bi 1.9(3) Sb 0.1(1) Te 3 Bi Bi Bi Te Bi 2 Te 3 Bi 1 5(3) Sb 0 5(1) Te 3 Bi 1.5(3) Sb 0.5(1) Te 3 1 1

Sample preparation and measurements � Sample Preparation Nanocomposite sawing Polishing ingot Rocking furnace (400 – 2000 - micro) � Measurements � Data Analysis 900 800 700 600 500 400 300 Seebeck Coefficient & Electrical 200 conductivity measurement conductivity measurement 300 300 400 400 500 500 600 600 700 700 800 800 Temperature(K) Nanocomposite 7 6 sample 5 4 3 2 1 300 400 500 600 700 800 Thermal conductivity measurement Temperature(K)

Nano-structured Bulk Therm oelectirc Material PbTe ingot with Bi 2 Te 3 nanoparticle + PbTe Bi 2 Te 3 nanoparticles(~150nm) incoherent interface Lattice Lattice Materials Structure parameter mismatch PbTe 6.3462A Rock salt 30% (a/a) a=4.385A, Rhomboh Bi 2 Te 3 c=30.48A edral PbTe with Bi 2 Te 3 2 3 ingot

Nano-Bulk Composite Thermoelectric Material PbTe ingot with Bi 2 Se 3 nanoparticle PbTe + Bi 2 Se 3 + + PbTe Bi 2 Se 3 nanoparticles(~80nm) Coherent(stress) Coherent(stress) i incoherent interface h t i t f

Nano-Bulk Composite Thermoelectric Material In 2 Te 3 ingot with Bi 2 Te 3 nanoparticle coherent interface + (Particle size < 20nm) In 2 Te 3 Matrix Bi 2 Te 3 nanoparticles (~150nm) (~150nm) In 2 Te 3 ingot with Bi 2 Se 3 nanoparticle + coherent interface In 2 Te 3 Matrix Bi 2 Se 3 nanoparticles (~80nm) 1 5

Nano-Bulk Composite Thermoelectric Material PbTe + 2.7% Bi 2 Te 3 PbTe + 10% Bi 2 Te 3 Composition dependent of electrical properties PbTe + 20% Bi 2 Te 3 2 3 PbTe + 2.7% bulk Bi 2 Te 3 Electrical Conductivity (S/cm) Seebeck Coefficient ( μ V/K) Power Factor ( μ W/cmK 2 ) -40 m) K) uctivity (S/cm fficient ( μ V/K 1200 10 2 ) -60 60 2 or ( μ W/cmK -80 1000 8 -100 -120 800 -140 6 -160 600 600 trical Condu ebeck Coef Power Facto -180 4 -200 400 -220 2 -240 200 -260 -280 0 See 0 0 P Elect 250 300 350 400 450 500 550 600 650 700 250 300 350 400 450 500 550 600 650 700 300 350 400 450 500 550 600 650 700 Temperature (K) Temperature (K) Temperature (K) � The values : � The values : � Negative value ~1000 S/cm at R.T. 1.5 ~9 W/cmK 2 � Majority of charge carriers : Electrons � The values : ~ -60~-220 μ V/K The values : 60 220 μ V/K Power Factor increase with decreasing nanoparticle content

Nano-Bulk Composite Thermoelectric Material tensity � Bulk Bi 2 Te 3 ative int * Bi 2 Te 3 ** * * * * * Rela 20 30 40 50 60 70 80 2 θ � Nanoparticle Bi 2 Te 3 sity ve intens Relativ 20 20 30 30 40 40 5 5 0 0 6 6 0 0 70 70 80 80 2 θ

1 Remove 1. Remove 2 Electrochemically deposition 2. Electrochemically deposition barrier oxide layer Bi nanowire material 3. Electrochemically deposition Te nanowire material 4. Remove AAO template AAO template

1 Remove 1. Remove 2 Electrochemically deposition 2. Electrochemically deposition barrier oxide layer nanowire material 1 Remove 1. Remove 2 Remove 2. Remove Ag film AAO template • Scheme 1. Schamatic of the process employed to produce (a) superlattice structure (b) one element or binary nanowire arrays by pulsed potential structure (b) one element or binary nanowire arrays by pulsed-potential deposition into porous anodic alumina template

SEM image Bi and Te NWs

Summary Summary Bulk에 나노입자, 나노선 삽입 열전재료용 나노입자, 나노선 제조 Hydrothermal법을 이용한 Bi 2 Te 3 의 morphologies PbTe ingot with Bi 2 Te 3 Colloidal법을 이용한 Bi 2 Te 3 나노입자 Bi 2 Se 3 나노입자 PbTe ingot with Bi 2 Se 3 PbTe ingot with Bi 2 Se 3 Sb 2 Te 3 나노입자 Bi x Sb 2 x Te 3 나노입자 Bi x Sb 2-x Te 3 나노입자 InTe ingot with Bi 2 Se 3 Bi 나노입자 CdSe 나노선 InTe ingot with Bi 2 Te 3 전기화학법을 이용한 Bi, Te 나노선

Conclusions • Nanostructured bulk CompositeTE materials Nanostructured bulk CompositeTE materials - New approaches are promising in raising ZT - Strong thermal conductivity reduction can be achieved through nanostructuring nanostructuring - Doping studies and processing conditions are important in ZT optimization • Nanoparticles - Nano particles of various TE materials are obtained • Nanocomposites - New approaches was provide to control the size and concentration of the nanocomponent in bulk TE materials the nanocomponent in bulk TE materials 2 2