New approaches to thermoelectric materials materials A.P. Gonalves - PowerPoint PPT Presentation

New approaches to thermoelectric materials materials A.P. Gonçalves ç Dep. Química, Instituto Tecnológico e Nuclear/CFMC-UL, P-2686-953 Sacavém, Portugal , g

Outline Outline � Introduction � New Systems � Conducting glasses C d i l � Bi doped Te Films p � Conclusions

ZT = S 2 T σ /K (adimensional, depends only on the material) S = Seebeck coefficient , σ = electrical conductivity, K = thermal conductivity ZT Efficiency or Coefficient of Performance maximization Performance maximization optimization optimization � Maximization of S 2 σ (power factor) f S 2 M i i ti ( f t ) � Minimization of K

Maximization of S 2 σ Maximization of S σ σ σ S S 2 σ S Insulators Metals Semiconductors 14 16 18 20 22 10 10 10 10 10 Carrier content concentration Carrier content concentration

Mi i Minimization of K i ti f K K = K elect + K lat Wiedemann-Franz law K elect = LT σ Decrease of K Decrease of K lat

Phonon-glass/electron-crystal (PGEC) materials G. Slack , in CRC Handbook of Thermoelectrics, 1995 Materials Approach h Effects on phonons ff h (examples) Heavy atoms weakly Skutterudites Phonon scattering centers Phonon-scattering centers bounded to the structures Clathrates Clathrates Complex structures Increase the optical phonon modes Yb MnSb Yb 14 MnSb 11 Increase diffusion Inclusions, impurities Inclusions impurities Composites Composites (affects more phonons than carriers) Increase mass fluctuations Increase mass fluctuations Half-Heusler Half Heusler Solid solutions (higher phonon scattering) systems Low dimensional G Grain boundaries i b d i R d Reduce the phonons mean free path th h f th systems

Matériaux thermoélectriques de type n Matériaux thermoélectriques de type n Type p thermoelectric materials In 0.2 Ce 0.2 Co 4 Sb 12 1.6 Ti 0.5 (Zr 0.5 Hf 0.5 ) 0.5 NiSn 0.998 Sb 0.002 Ba 8 Ga 16 Ge 30 LaTe 1.45 1.4 In 0.2 Co 4 Sb 12 Ba 0.3 Co 3.95 Ni 0.05 Sb 12 1.2 Bi 2-x Sb x Te 3 2-x x 3 b Pb 1-x Sn x Te 1-y Se y 1.0 3 S Si 0.80 Ge 0.20 o C ZT 0.8 0.8 Z (Zn 0.98 Al 0.02 )O - UFP Bi 2 (Sb,Te) 3 0.6 0 4 0.4 SrPbO 3 β -FeSi 2 0.2 0.0 0 200 400 600 800 1000 1200 1400 Température (K) Température (K)

Materials Materials Approach Approach Effects on phonons Effects on phonons (examples) (examples) Heavy atoms weakly Heavy atoms weakly Heavy atoms weakly Heavy atoms weakly Skutterudites Skutterudites Skutterudites Skutterudites Phonon-scattering centers Phonon-scattering centers bounded to the structures bounded to the structures Clathrates Clathrates Gl Glasses Clathrates Clathrates Clathrates Clathrates Complex structures Complex structures Increase the optical phonon modes Increase the optical phonon modes Yb 14 MnSb 11 Yb 14 MnSb 11 Increase diffusion Increase diffusion d ff d ff Inclusions, impurities Inclusions, impurities Composites Composites (affects more phonons than carriers) (affects more phonons than carriers) Increase mass fluctuations Increase mass fluctuations Half-Heusler Half-Heusler Solid solutions Solid solutions (higher phonon-scattering) (higher phonon-scattering) systems systems Low dimensional Low dimensional Grain boundaries Grain boundaries Reduce the phonons mean free path Reduce the phonons mean free path systems systems

Conducting Glasses Conducting Glasses Minimization of K Low K lat Maximization of S 2 σ

Metallic Glasses Metallic Glasses Author(s): LINKESOVA, V; VESELSKY, J Title: TEMPERATURE-DEPENDENCE OF THE SEEBECK COEFFICIENT AND OF METALLIC- GLASS ELECTRIC-RESISTANCE Source: ACTA PHYSICA SLOVACA, 35 (1): 40-46 1985 Author(s): BHATNAGAR, AK; PRASAD, BB; RATHNAM, NRM 4 < T < 1000 K T Title: MAGNETIC, ELECTRICAL AND THERMOELECTRIC STUDIES ON METALLIC-GLASS Title: MAGNETIC ELECTRICAL AND THERMOELECTRIC STUDIES ON METALLIC GLASS 4 1000 K FE39NI39MO4SI6B12 Source: JOURNAL OF NON-CRYSTALLINE SOLIDS, 61-2 (JAN): 1201-1206 1984 Author(s): PEKALA, K; PEKALA, M; TRYKOZKO, R Title: MAGNETIC THERMOELECTRIC-POWER OF FE20NI60B10SI10 METALLIC-GLASS 0 < ⏐ S ⏐ < 5 µ V/K Source: SOLID STATE COMMUNICATIONS, 46 (5): 413-415 1983 Author(s): CARINI, JP; BASAK, S; NAGEL, SR; GIESSEN, BC; TSAI, CL Title: THE THERMOELECTRIC-POWER OF THE METALLIC-GLASS CA0.8AL0.2 Source: PHYSICS LETTERS A, 81 (9): 525-526 1981 Author(s): TEOH, N; TEOH, W; ARAJS, S; MOYER, CA Title: ABSOLUTE THERMOELECTRIC POWER OF AMORPHOUS METALLIC GLASS FE80B20 Title: ABSOLUTE THERMOELECTRIC-POWER OF AMORPHOUS METALLIC GLASS FE80B20 BETWEEN 300-K AND 1000-K Source: PHYSICAL REVIEW B, 18 (6): 2666-2667 1978 Author(s): NAGEL, SR Title: THERMOELECTRIC-POWER AND RESISTIVITY IN A METALLIC GLASS Source: PHYSICAL REVIEW LETTERS, 41 (14): 990-993 1978

Nb Ni Sn Nb 32 Ni 60 Sn 8 S l t Splat cooling li

Nb 32 Ni 60 Sn 8 400 300 (a.u.) Intensity 200 100 0 10 20 30 40 50 60 2 θ (º) S (300 K) = 1 1 µ V/K S (300 K) = 1.1 µ V/K

Semiconducting Glasses Semiconducting Glasses

Ge 20 Te 80 - known glass Ge 20 Te 80 known glass semiconductor; Quenching in ice water; Q g T g = 428 K, T c = 493.5 K [1] ; , g c S(300 K) = 960 µ V/K S(300 K) = 960 µ V/K, ρ (300 K) = 2.77x10 8 µΩ µΩ m [2] . [1] M Abu El Oyoun J Phys D: Appl Phys 33 (2000) 2211 2217 [1] M Abu El-Oyoun, J. Phys. D: Appl. Phys. 33 (2000) 2211–2217. [2] G. Perthasarathy, A.K. Bandyopadhyay, S. Asokan, E.S.R. Gopal, Solid State Commun. 51 (1984) 195-197.

Ge 20-x Te 80-y M x+y ρ decrease? M = Ag, Cu [1,2] Cu x Ge y Te z general compositions; C Cu 25 T 5 Te 70 (T = Si, Ga) T T (T G ) [1] A. Ferhat, R. Ollitrault-Fichet, V. Mastelaro, S. Bénazeth, J. Rivet, J. de Physique IV, 2 (1992) C2-201-C2-206. y q ( ) [2] K. Ramesh, S. Asokan, K.S. Sangunni, E.S.R. Gopal, J. Phys.: Condens. Matter 8 (1996) 2755-2762.

• Preparation by melt-spinning;

Cu 30 Te 70 1500 1500 1500 1500 Cu 15 Ge 10 Te 75 Cu Ge Te Cu Ge Te Cu 15 Ge 10 Te 75 u.) u.) Cu 7 5 Ge 15 Te 77 5 Cu 7 5 Ge 15 Te 77 5 7.5 7.5 15 15 77.5 77.5 ty (a.u ty (a.u Ge 20 Te 80 Ge 20 Te 80 1000 1000 ntensi ntensi 500 500 I 0 0 20 20 30 30 40 40 50 50 60 60 2 θ (º) 2 θ (º) 2 θ ( ) 2 θ ( )

DTA 0 T c Cu 20 Ge 5 Te 75 Cu Ge Te -2 -0.5 T c u.) u.) ux (a.u ux (a.u Cu 20 Ge 5 Te 75 -4 Heat Fl Heat Fl T g -6 -1.0 H H -8 320 50 100 330 150 340 200 350 250 360 Temperature (ºC) Temperature (ºC)

10 10 10 10 Cu 20 Ge 5 Te 75 9 10 Cu 15 Ge 7,5 Te 77,5 Cu 25 Ga 5 Te 70 8 10 Cu 22,5 Ge 2,5 Te 75 7 10 10 µΩ m) ) Cu 25 Si 5 Te 70 ρ ( µΩ 6 10 Cu 27.5 Ge 2.5 Te 70 Cu Ge Te ρ 5 10 4 10 3 10 4 6 8 10 12 14 -1 ) 1000/T (K

1000 µ V/K) Cu 15 Ge 7.5 Te 77.5 power ( µ Cu 22.5 Ge 2.5 Te 75 Cu 27.5 Ge 2.5 Te 70 Cu 20 Ge 5 Te 75 500 Thermop Cu 25 Si 5 Te 70 Cu 25 Ga 5 Te 70 T 100 100 200 200 300 300 T(K)

8 10 7 10 ( µΩ m) ) 6 10 ρ 300 K ( 5 10 ρ 4 10 3 10 70 72 74 76 78 80 T Te % %

8 10 7 10 ( µΩ m) ) 6 10 ρ 300 K ( 5 10 ρ 4 10 3 10 2 4 6 8 10 12 14 16 18 20 22 Ge % Ge %

8 10 7 10 ( µΩ m) ) 6 10 ρ 300 K ( 5 10 ρ 4 10 3 10 0 5 10 15 20 25 30 Cu %

1000 800 V/K) 600 S ( µ V 400 200 0 70 72 74 76 78 80 Te %

1000 800 V/K) 600 S ( µ V 400 200 0 2 4 6 8 10 12 14 16 18 20 22 Ge %

1000 800 V/K) 600 S ( µ V 400 200 0 0 5 10 15 20 25 30 Cu %

60 2 m) ( µ W/K K 40 2 / ρ ( 20 S 0 0 70 72 74 76 78 80 Te %

60 2 m) ) W/K ρ ( µ W 40 2 / ρ S 20 0 0 2 4 6 8 10 12 14 16 18 20 22 Ge %

60 m) 2 m 40 W/K 2 / ρ ( µ W 20 2 S 0 0 0 5 10 15 20 25 30 Cu %

S 2 / ρ S / ρ ρ 300K ρ 300K Glass Glass E (Hi h T) E a(High T) S 300K S 300K ( µΩ m) ( µ V/K) ( µ WK -2 m -1 ) Composition (meV) Cu 25 Ge 5 Te 70 1000 - 150 22.5 Cu 25 Ga 5 Te 70 2540 134 344 47 Cu 25 Si 5 Te 70 5150 125 357 25

Conducting Glasses - Conclusions • Close to crystallization; Cl s t cr st lliz ti n; • Semiconductor and semimetal behavior; • High Seebeck values; • Moderately high resistivities; • Low gap; • Cu increases → Power factor increases; Cu increases → Power factor increases; • Good potential for thermoelectric applications.

Bi doped Te Films Bi doped Te Films • Many good Te-based thermoelectric materials; d b d h l i i l S. Deng, J. K¨ohler and A. Simon, Physica C 460–462 (2007) 1020– 1021.

• Low Te bulk thermal conductivity (2.35 Wm -1 K -1 [T=300 K ]). Maximization of S 2 σ