Marta Rull-Bravo 1,* , Alberto Moure 2 , Begoña Abad 2 , Miguel Muñoz Rojo 2 , Alexander Jaquot 3 , Adolfo del Campo 2 , José Francisco Fernández 2 , Marisol Martín González 1 Tailoring the thermoelectric properties of Skutterudites by nanocomposites 1 Microelectronics Institute of Madrid, CSIC, 28760 Tres Cantos, Madrid, Spain 2 Instituto de Cerámica y Vidrio, CSIC, 28049, Madrid, Spain 3 Fraunhofer-IPM, 79110 Freiburg, Germany *[email protected] 34 th ANNUAL INTERNATIONAL CONFERENCE ON THERMOELECTRICS 13 th EUROPEAN CONFERENCE ON THERMOELECTRICS Skutterudites have attracted great attention for their promising potential on thermoelectric applications, such as harvesting the heat generated in industrial processes and automotive operations. To improve their thermoelectric figure of merit ,emphasis has gone into modifying the band structure through doping to enhance the Power Factor and reducing thermal conductivity through increasing phonon scattering by filling and in-situ nanocomposites formation. 1 Depending on the nature of the nanoinclusions and the proportion in the matrix, it is possible to tailor the thermoelectric properties. 2 In this work, different concentrations of oxides were included in a one-step synthesis mechanism, obtaining the Skutterudite phase with nanoinclusions and therefore, achieving lower thermal conductivities than those reported in literature. Synthesis of CoSb 3 -alloys were performed by High Energy Ball Milling and compaction by Spark Plasma Sintering, resulting in the formation of a cobalt antimonide nanocomposite. The high amount of interfaces achieved increases the phonon scattering and reduces the thermal conductivity to values around 2 Wm -1 K -1 . Doping with tellurium increases the power factor. By using both approaches together, the thermoelectric properties are highly increased by effective decoupling of thermal and electrical properties. Acknowledgements: European Commission under the Seventh Framework Programme (FP7) Grant # 263167 References : [1] Shi, X. et al. Multiple-Filled Skutterudites: High Thermoelectric Figure of Merit through Separately Optimizing Electrical and Thermal Transports. Journal of the American Chemical Society 133, 7837-7846 (2011) [2] Zhao, X. et al. Synthesis of Yb y co 4 sb 12 /Yb 2 o 3 Composites and Their Thermoelectric Properties. Applied Physics 6, 89, 092121 (2006) [3] Rull - Bravo,M . et al. Skutterudites as Thermoelectric Materials: Revisited. RSC Advances 5, 41653 - 41667 (2015) 1995 2000 2005 2010 2015 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 zT Year n-type p-type Reduce k by nanocomposites segregation Increase S 2 s by doping State of the art in Skutterudites 3 Sb Te d 1 d 2 d 1 d 2 Approaches to enhance CoSb 3 figure of merit 20 30 40 50 60 70 80 Intensity (a.u.) 2 (degree) 0 h 1 h 4 h 6 h 14 h 15 h 552 550 444 631 622 532 442 433 431 422 332 420 330 321 310 211 CoSb 3 ● Sb 2 O 3 ◊ CoSb 2 ● ◊ ◊ 5.0 μm 100 200 300 400 500 600 700 800 Intensity (a. u.) Raman shift (cm -1 ) CoSb 3 CoSb 2 O 4 Sb 2 O 3 +CoSb 3 E g A g T g T g A g T g T g X-Ray diffraction and Raman confirm the presence of CoSb 3 phase and CoSb 2 O 4 and Sb 2 O 3 as secondary phases. Nanostructuring in the nanopowder was confirmed by TEM images. CoSb 3 phase and oxide segregation and their different electrical conductivity behaviors were confirmed with topographical and current maps measured by AFM. 300 400 500 600 700 800 900 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 zT Temperature (K) CoSb 3 x=0,05 x=0,15 x=0,2 300 400 500 600 700 800 900 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 CoSb 3 Thermal conductivity (W/m.K) Temperature (K) x=0,15 x=0,2 x=0,05 300 400 500 600 700 800 0.0015 0.0020 0.0025 0.0030 0.010 0.015 0.020 x=0,1 x=0,15 CoSb 3 Resistivity (cm) Temperature (K) x=0,05 x=0,2 300 400 500 600 700 800 900 -400 -360 -320 -280 -240 -200 -160 -120 -80 -40 CoSb 3 Seebeck coefficient (V/K) Temperature (K) x=0,2 x=0,15 x=0,05 x=0,1 300 400 500 600 700 800 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Temperature (K) zT CoSb 3 nanocomposite CoSb 2,85 Te 0,15 300 400 500 600 700 800 10 -3 10 -2 0 2 4 6 8 CoSb 2.85 Te 0.15 nanocomposite CoSb 3 CoSb 2.85 Te 0.15 Temperature (K) Resistivity (·cm) nanocomposite CoSb 3 Thermal conductivity (W/(m.K)) Thermoelectric properties of Te-doped CoSb 3 nanocomposite CoSb 3-x Te x zT=1 Decoupling electrical and thermal conductivity, through doping and nanostructuring, leads to an enhance the figure of merit. For CoSb 2.85 Te 0.15 compound a zT of 1.0 at 750K is achieved. 0.00 0.00nA -99.42nA X-Ray diffraction SEM/TEM Optical image Raman C-AFM