Transcript Thermoelectric properties in the series AgxTiS2

Thermoelectric properties in
the series AgxTiS2
Tristan Barbier, Marine Beaumale, Oleg Lebedev, Emmanuel
Guilmeau, Yohann Bréard, Antoine Maignan
[email protected]
Laboratoire CRISMAT, UMR6508 CNRS ENSICAEN,
6 bd du maréchal Juin, 14050 CAEN
ECT 2013 - ESA/ESTEC, Noordwijk
Summary

Introduction

AgxTiS2 synthesis and sintering

Microstructure analysis

Thermoelectric properties

Conclusion
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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 thermoelectric generators based on:
Low cost / abundant precursors
Low density of both compounds (n- p-types)
Non-toxic elements
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The purpose is 30 Wp/m² => ≈ 600€ / kWp (PV ≈ 3000€ / kWp)
ZT ≈ 0.5 @ 100°C – T° range < 100°C - ∆T ≈ 30-80°C
Introduction
In order to reach the full project specifications, TiS2 was chosen because :
Low price : 4.55 €/kg ( < 5.20 €/kg)
Price: 40€/kg
Low density : 3.24 g.cm-3
High density: 7.7 g.cm-3
Bi2Te3
Abundant precursors
Non-toxic precursors and final compound Toxic
Ti
S
Ag
Ti
S c
Currently, the best ZT value of TiS2 is around 0.20 @ 100°C - 0.37 @ 500°C*.
=> Improve the thermoelectric properties of TiS2.
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=> AgxTiS2 with x = 0.02 ; 0.05 ; 0.1 and 0.2
*E. Guilmeau, Y. Bréard and A. Maignan, Applied Physics Letters 99, 052107 (2011)
AgxTiS2 synthesis and sintering
Agx
Ti
S
Sealed silica
tube
630°C
12h
Grind
Muffle Furnace
Sieve
600°C
30 min
76 Mpa
SPS
Densities of the final pellets > 97%
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All compounds with x < 0.2
contain only two phases
Ag0.167TiS2 and TiS2
Microstructure analysis : HR XRD
Modelling with isotropic crystallite size
(110)
(102)
(h,k < l)
(h,k > l)
Modelling with anisotropic crystallite size
(00l)
(110)
χ² = 3.00
RBragg = 5.42
(102)
Platelet-like grains
χ² = 5.89
RBragg = 8.90
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Microstructure analysis : HR XRD
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Thermoelectric properties
All the thermoelectric properties were measured along the pressure direction
ISIEM 2013 – 27-31 October, Rennes
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The resistivity and |S| values decrease showing that charge carriers
concentration is increased by the Silver intercalation
Thermoelectric properties
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Thermoelectric properties
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Conclusion
 Silver
intercalation leads to an increase of the charge carriers
concentration
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 TiS2 in all the
temperature range.
Prospects

Synthesis of compounds with lower content of silver (< 0.02)

Synthesis of compounds with different cationic intercalation (Bi, Co…)
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Acknowledgement
Thank you for your attention
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Microstructure analysis : HR XRD
h
k
(110)
(00l)
(102)
(hk0)
(h,k < l)
(h,k > l)
(110)
When (h,k <l) the thickness of the platelike is thin.
=> So the crystallization domain is lower
than the theorical one.
The real peak is more wide and less
intense.
l
(102)
Modelling with isotropic crystallite size
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Microstructure analysis : HR XRD
Microstrain calculation :
1) Williamson et Hall
β cos (θ)
β cos (θ) = f ( sin (θ) )
Slope = Microstrain
Intercep = Crystallite size
sin (θ)
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Microstructure analysis : HR XRD
LaB6 refinement using Caglioti law
Creation of .IRF file => U, V, W, X, Y, Z = 0
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Microstructure analysis : HR TEM
Ag0.2TiS2
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Ag0.1TiS2
Ag0.2TiS2