Evaluation systems of thermoelectric properties of electrochemically - - PowerPoint PPT Presentation

Evaluation systems of thermoelectric properties of electrochemically deposited Bi2Te3 films and nanowire arrays

Yoshikazu Shinohara*, Marisol Martin-Gonzalez**

* National Institute for Materials Science, Japan

** Instituto Microelectrónica de Madrid, Spain

The state of arts of thermoelectric materials

ドーピング制御 化合物組成比探索 人工超格子 移動度大の 化合物半導体 ラットリング ス クッ テル ダイト 系 クラス レ ート 系 ハ ーフ ホイス ラ系 ｆ 電子強相関系 多結晶体制御 固溶体系 量子効果



性能指数 S：ゼーベック係数（µV/K） ρ:比抵抗（Ωm) κ:熱伝導率（W/Km)

κ ρ

2

S Z =

ZT

SrTiO3 PbSeT e Bi2T e3 /Sb2T e3

材料系 ↑ プロセス

Film Bulk

Superlattice Quantum effect Ratlling Poly-crystal Doping Composition

Process control Materials

Compound semiconductors Solid solutions Sukuttledite Clathrate Half-whistler Strong corellated

κ σ T S ZT

2

=

S：Seebeck coefficient（µV/K）

σ：Electrical conductivity (S/m）

κ：Thermal conductivity（W/Km） T： Absolute temperature (K)

Dimensionless figure-of-merit

Dilemma between nanotechnology and macro application(waste heat recovery)

Nano technoplogy Micro technology Macro technology Physics Computer Science Material Science Material Process Try and Error Device Process

How to overcome the dilemma?

Research Field: “Nanoscience and New Materials for Environmental Challenges”

Cooperative Research Project (2010-2012) First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA-

FY2009 Strategic Japanese-Spanish Cooperative Program

Goal

(1) Developing thermoelectric technologies of nanowire arrays. (2) Finding a hint for a breakthrough of thermoelectric performance.

Synthesis Technology Measurement Technology

+

Bi-Te nanowire array Quantitative evaluation

Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara

Instituto Microelectrónica de Madrid National Institute for Materials Science Spain Japan

Exchange of technology, idea and researchers

Good cooperation in the near future

Samples

Not Annealed 423 K/1 hr 473 K/1 hr 573 K/1 hr

1 μm ×20000

Bi2Te3 film Bi2Te3 nanowire array

1.3 cm Alumina template.

120nmφ

Experimental Setup for films (in-plane direction)

Measurement of Seebeck coefficient for Standard sample (Pt wire)

The measured value agrees well with the reference value of -5.24µV/K

All resistance measured with probe distance ~ 5 mm

Seebeck coefficient (µV/K) Electrical conductivity (S/cm)

Samples Experiments Asprepared 423 K 473 K 573 K Substrate Si/Ti/Au Measured resistance 0.23 Ω 0.14 Ω 0.15 Ω 0.28 Ω 1.81 Ω Seebeck coefficient

• 4.57 µV/K
• 6.58 µV/K
• 6.36 µV/K
• 9.33 µV/K
• 104.47 µV/K

(273K)

:Heat sink :Sample stage with thermocouple :Peltier heater :Sample

• Fig. Sample stage with thermocouple

Thermocouples: T-type 0.127 mmφ Peltier heater: 4cm×４cm Max. input ６W

Experimental Setup for nanowire array (thickness direction)

Seebeck coefficient Standard measurement using Si wafer (thickness 500 μm)

0.0 0.5 1.0 1.5 2.0 20 40 60 80 100 120 140

y = 0.012143 + 0.016536x R= 0.99984

Temperature deference / K Input power of heater x / mW

• Fig. Temperature difference as a function
• f input power.
• Fig. Home-made apparatus of

nanowire array measurement

Temperature difference /K

• 600
• 450
• 300
• 150

0.5 1 1.5 2 2.5 3

y = = -5. 5.916 169 -

• 18

186.3 .38x x R R= 0 0.99 99997 97

Total thermoelectric power / μV Delta T / K

• 600
• 500
• 400
• 300
• 200
• 100

0.5 1 1.5 2 2.5 3 Total thermoelectric power / μV Delta T / K

⊿T ⊿T Ssi=-179.96 μVK-1

Seebeck coefficient of standard measurement using Si wafer

• Fig. Relationship between deltaT and

total thermoelectric power(TPtotal) in thickness direction of Si.

• Fig. Relationship between deltaT and

total thermoelectric power(TPtotal) in planar direction of Si.

Good matching between in-plane and thickness setups

In-plane setup Thickness setup

Thermoelectromotive force /µV Thermoelectromotive force /µV

Ssi=-184.52 μVK-1

Seebeck coefficient and electrical conductivity

• f Bi2Te3 nanowire array

5 10 15 20 25 5 10 15 20 25 30 35 Thermoelectric power / μV Input power of heater / mW 厚さ60 μm

• Fig. Thermoelectric power as a function
• f input power.

S=12µV/K

Thermoelectromotive force /µV

Seebeck coefficient of films

5 10-5 1 10-4 2 10-4 2 10-4 5 10-6 1 10-5 1.5 10-5 2 10-5 2.5 10-5

y = 3.5e-7 + 7.708x R= 0.99991

Voltage / V Current / A

1 4

10 79 . 1

− −

× = Scm σ

• Fig. I-V curve of nanowire-array.

1.3 cm Alumina template.

Good cooperation in the near future

Research Field: “Nanoscience and New Materials for Environmental Challenges”

Cooperative Research Project (2009-2012) First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA-

FY2009 Strategic Japanese-Spanish Cooperative Program

Synthesis Technology Measurement Technology

+

Bi-Te nanowire array Quantitative evaluation

Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara

Instituto Microelectrónica de Madrid National Institute for Materials Science Spain Japan

Exchange of technology, idea and researchers

Good results by good collaboration between Japan and Spain

Acknowledgment

• Dr. Yukihiro Isoda
• Dr. BISWAPRIYA DEB
• Dr. Hiroshi Kawakami
• Dr. Olga C. Calero
• Dr. Pablo Díaz Chao
• Ms. Begona A. Mayor

(Best poster award at the Workshop at Toledo in 2011)

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