Thermoelectric properties in the series Ag x TiS 2 Tristan Barbier, Marine Beaumale, Oleg Lebedev, Emmanuel Guilmeau, Yohann Bréard, Antoine Maignan Laboratoire CRISMAT, UMR6508 CNRS ENSICAEN, 6 bd du maréchal Juin, CAEN ECT ESA/ESTEC, Noordwijk

Summary  Introduction  Ag x TiS 2 synthesis and sintering  Microstructure analysis  Thermoelectric properties  Conclusion 2

3 Introduction This study is performed in the framework of InnovTEG project. An innovative very low-cost thermo-electric technology for large-scale renewable solar energy applications The aim of this project is to create thermo- electric generators based on: Low cost / abundant precursors Low density of both compounds ( n- p- types) Non-toxic elements The purpose is 30 Wp/m² => ≈ 600€ / kWp (PV ≈ 3000€ / kWp) ZT ≈ 100°C – T° range < 100°C - ∆T ≈ 30-80°C

4 Introduction *E. Guilmeau, Y. Bréard and A. Maignan, Applied Physics Letters 99, (2011) In order to reach the full project specifications, TiS 2 was chosen because : Non-toxic precursors and final compound Low price : 4.55 €/kg ( < 5.20 €/kg) Abundant precursors Low density : 3.24 g.cm -3 Currently, the best ZT value of TiS 2 is around 100°C - 500°C *. => Improve the thermoelectric properties of TiS 2. Ag => Ag x TiS 2 with x = 0.02 ; 0.05 ; 0.1 and 0.2 Ti S S c Bi 2 Te 3 Toxic High density: 7.7 g.cm -3 Price: 40€/kg

5 Ag x TiS 2 synthesis and sintering Ag x Ti S Sealed silica tube 630°C 12h Muffle Furnace Grind Sieve 600°C 30 min 76 Mpa SPS Densities of the final pellets > 97% All compounds with x < 0.2 contain only two phases Ag TiS 2 and TiS 2

6 Microstructure analysis : HR XRD Platelet-like grains (110) (102) Modelling with isotropic crystallite size (h,k < l) (h,k > l) Modelling with anisotropic crystallite size (00l) (102) (110) χ² = 5.89 R Bragg = 8.90 χ² = 3.00 R Bragg = 5.42

7 Microstructure analysis : HR XRD

ISIEM 2013 – October, Rennes 8 Thermoelectric properties All the thermoelectric properties were measured along the pressure direction The resistivity and |S| values decrease showing that charge carriers concentration is increased by the Silver intercalation

9 Thermoelectric properties

10 Thermoelectric properties

 Silver intercalation leads to an increase of the charge carriers concentration 11 Conclusion Decrease of the resistivity Decrease of Seebeck coefficient  Silver intercalation: creation of crystallographic disorder Decrease of the thermal conductivity: ZT values of x = 0.02 sample is higher than TiS 2 in all the temperature range. Prospects  Synthesis of compounds with lower content of sil ver (< 0.02)  Synthesis of compounds with different cationic intercalation (Bi, Co…)

12 Acknowledgement Thank you for your attention

13 Microstructure analysis : HR XRD (h,k < l) (h,k > l) When (h,k <l) the thickness of the plate- like is thin. => So the crystallization domain is lower than the theorical one. The real peak is more wide and less intense. (00l) h k l (hk0) (110) (102) Modelling with isotropic crystallite size (102) (110)

14 Microstructure analysis : HR XRD Microstrain calculation : 1) Williamson et Hall β cos (θ) = f ( sin (θ) )β cos (θ) sin (θ) Slope = Microstrain Intercep = Crystallite size

15 Microstructure analysis : HR XRD LaB 6 refinement using Caglioti law Creation of.IRF file => U, V, W, X, Y, Z = 0

16 Microstructure analysis : HR TEM Ag 0.1 TiS 2 Ag 0.2 TiS 2