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THERMOELECTRIC MATERIAL AND DEVICE.
1. Guide:-
Mr. Sankalp Kulshrestha
Assistant Professor
SGVU, Jaipur
Synthesis of High ZT Materials and
Module Fabrication
Dalvir Singh
M.TECH(EE)
SGVU101254341
Co-guide:-
Dr. T.D. Senguttuvan
Principle Scientist
NPL, Delhi
2. :
•Development of n-type (Bi2Te3) TE material suitable for low temperature
applications with high ZT
•Development of p-type (Sb2Te3) TE material suitable for low temperature
applications with high ZT
• Demonstration of thermoemf by combining the above mentioned n- and p-
type TE materials
Objectives
3. Introduction
What is TEG ?
Device that convert temperature Differences into electrical energy.
Basic principles - Seebeck effect
Heat input
Hot junction
Cold
junction
P-type N-type
Heat ejection
Power output
when the junctions of two different metals are
maintained at different temperature, the emf is
produced in the circuit.
Based on above phenomenon, waste heat recovery
could be utilized to produce useful electricity
4. Why choose Bismuth telluride and Antimony Telluride
1. Low Cost
2. High Electrical conductivity
3. Low Toxic
4. Easily available
5. Performance of a Thermoelectric(TE) material is defined by ZT given as :
A good thermal material must have
1. High seebeck coefficient
2. High electrical conductivity
3. low thermal conductivity
6. 1. n-type TE material: Bismuth telluride (Bi2Te3)
Solvothermal Route
Mixed Bi and Te precursors, reducing agent, vessel filled upto 85% solvent
Check pH
Sealed the autoclave immediately and heated up to 1900C for 24h
Filtered the obtained precipitate, washed several times with distilled water,
ethanol, acetone and then dried in vacuum
Bi2Te3 powder
7. Fig.: XRD pattern of the as prepared samples using different solvents. All peaks indexed to hexagonal Bi2Te3
phase for methanol as a solvent
Fig.: SEM images of as prepared products with methanol as a solvent
(a) low and (b) high magnification
8. Bi2Te3 powder
HP at 4000C for 6 Hour under vacuum
Measure TE properties
HOT PRESSING
300 350 400 450 500 550 600
0.25
0.30
0.35
0.40
0.45
ZT
T(K)
• ZT=0.42 at 197˚C which comparatively less than best reported ZT (0.7) at 180C by hydrothermal
route (Fu et.al, CrystEngComm, 2012, 14, 2159)
• The main reason for less ZT value is the high thermal conductivity (). [ should be <1]
• This is due to the increased particle size -consequence of heat treatments.
• To decrease the value of thermal conductivity, some nano-range boundaries need to be introduced so
as to increase the phonon scattering. Bi2Te3 + BiTe (in different mol%)
Ref. => PbTe-SrTe(4mol%) [Biswas et.al, Nature, 489 (2012)] ZT increased to 2.2 from 1.7
12. Solvothermal Route
Mixed Sb and Te precursors, reducing agent, vessel filled upto 85% solvent
Check pH
Sealed the autoclave immediately and heated up to 1900C for 24h
Filtered the obtained precipitate, washed several times with distilled water,
ethanol, acetone and then dried in vacuum
Sb2Te3 powder
2. p-type TE material: Antimony Telluride (Sb2Te3)
13. Fig.: XRD pattern using different solvents.
Water gave rhombohedral Sb2Te3 phase
XRD Analysis
10 20 30 40 50 60 70 80
Te
(0123)
(300)
(2110)
(0216)
(1019)
(125)
(0210)
(0018)
(205)
(119)
(1013)
(0015)
(110)
(0111)
(1010)
(018)
(015)
2degrees)
Sb
Sb
Sb
methanol
water
(006)
(0120)
Intensity(arb.units)
Te
15. Sb2Te3 powder
HP at 3000C for 6 Hour under vacuum
Measure TE properties
HOT pressing
320 360 400 440 480
0.1
0.2
0.3
0.4
0.5
0.6
ZT
T(K)
Our work
Dong.et.al, J.Mater.Chem, 2010
•Dong et.al reported ZT=0.58 at 420K Microwave assisted solvothermally
synthesized Sb2Te3
•To further increase ZT, PbTe (50-150nm) in different mol% mixed in Sb2Te3
powder(200-300nm)
References:
Li et.al, Appl. Phy. Lett., 104, 113905(2014); ZT=1.54 at 723K was obtained
for AgPbmSbTem+2 with 1 vol.% SiC nanoparticles
PbTe-SrTe(4mol%) [Biswas et.al, Nature, 489 (2012)], ZT increased to 2.2
from 1.7
20. 3. Demonstration of thermo-emf using n- and p- type TE material
n- and p-type
TE material-
21. Furnace
Temperature(F.T)
(oC )
Hot Side
Temperature(TH)
(oC )
Cold Side
Temperature(TC)
(oC )
∆T
(oC )
Voltage
(mV)
Sensitivity
(mV/oC)
100 43 36 07 2.14 0.305
200 88 49 39 4.02 0.103
300 133 61 72 6.6 0.091
400 152 72 80 8.5 0.106
Furnace
Temperature(F.T)
(oC )
Hot Side
Temperature
(TH)
(oC )
Cold Side
Temperature(TC)
(oC )
∆T
(oC )
Voltage
(mV)
Sensitivity
(mV/oC)
100 48 34 12 1.55 0.129
200 92 42 50 5.25 0.105
300 140 48 92 10.85 0.117
400 168 72 96 17.8 0.185
Pure TE Material
Composite TE Material
22. The n-type (Bismuth Telluride) and p- type (Antimony
Telluride) materials were successfully synthesized
using Solvothermal route. XRD, SEM and TEM were
used to characterize as prepared samples for phase,
morphology and particle size
The thermo e.m.f was measured for the fabricated
module using both pure and composite materials.
