Transcript Prospective Thermoelectric Tellurides

E2.1.8x6761
Prospective Thermoelectric
Tellurides
Patrik Čermák
University of Pardubice, Czech Republic
„Thermoelectrics as an ‘energy gate’ to deep space“
Space probes (e.g.):
• Voyager 1, 2 (1977)
• Galileo
(1989)
• Ulysses
(1990)
• Cassiny
(1997)
• New Horizons (2006)
I. Introduction to Thermoelectrics
1.
Seebeck effect
2.4 Peltier effect
Cooling
n - Bi2Te2.95Se0.05
-1
U AB   AB T
3
n - PbTe
p-type
+
+
+
- n-type
-
+U -
Thermoelectric materials
•
The main aim of researching
of TE materials in general
is enhance their efficiency in
defined temperature range.
2
p-type
1
- - -
Q  TI
p - Zn4Sb3
p - Ce Fe0.9Co0.1Sb3
3
Heating
Z*10 (K )
p - Bi0.5Sb1.5Te3
+
+
+
n - SiGe
- p - SiGe
n-type
Q ZT = 1
0
500
1000
T (K)
Performance criterion for practical
applications:
 2T
ZT 

1500
II. Research
Motivation
Bi2Te3
1. Optimize of figure of merit ZT of n-type Bi2+xTe3-x-y-zSeyIz
polycrystalline system for enhance of efficiency of
Peltier elements in room temperature range (300 K).
a
2. Preparation of „novel TE material – GaGeTe“ with
enhanced electrical conductivity  (focuse on figure of
merit ZT) and development of complementary n-type.
Te 1
Te 1
Sb
Bi
Te 2
Sb
Bi
Characterization
•
•
X-ray Diffraction
Seebeck coefficient 
(Tc)
•
Electrical conductivity c
•
Thermal conductivity 
•
Hall coefficient RH (B║c)
Te 1
GaGeTe
c
Te 1
Sb
Bi
Te 2
Sb
Bi
Te 1
III. Results
Bi2+xTe3-x-y-zSeyIz
GaGeTe1-xIx
280
260
240
220
430 K
 (V/K)
200
180
160
140
120
100
GaGeTe (no tempering)
Bi0,5Sb1,5Te2,9Se0,1
80
60
50
100
150
200
250
T (K)
300
350
400
450
IV. Discussion
Bi2+xTe3-x-y-zSeyIz
The samples with tetradymite structure were prepared. For optimization
of TE properties (focused on figure of merit ZT) was examined the
influence of iodine by doping classical Bismuth-Telluride (Bi2Te3).
Iodine +1-e than Tellurium  increment of the concentration of free
charge carriers:
Substitution of „Te“ for „I“ - Bi2+xTe
n 3-x-y-zSeyIz:
n



GaGeTe1-xIx
T
This (ternary) system show high Seebeck coefficient then the state-ofthe-art materials.
Is it a p-type semiconductor  n-type = more –e.
I have prepared substitute compound TeI4 and doped the GaGeTe.
XRD shows minimal content of other phases  successful doping.

VTeTe
V. Conclusions
Bi2+xTe3-x-y-zSeyIz
The character of the optimize TE material is possible to expect at

Bi2Te2,9Se0,096I0,004 – lower concentration of iodine but also VTe
.
Now will follows the measurements of the other TE properties
including „certainty“ identifications by XRD.
GaGeTe1-xIx
The first results promising great potential of this „novel ternary
telluride“.
Will follows the continual research consists from: (1) increment
value of iodine for development complementary n-type, (2) doping
by another elements which can increment value of electrical
conductivity (e.g. create defects of positive charge) and then
optimized its TE efficiency (parameter ZT).
Thank you for your attention
References for this presentation
Image „Stargate SG-1“
[1] www.trekkies.cz
Images of the space probes
[2] www.nasa.gov, www.wikipedia.org
Image „Radioisotope Missions“
[3] www.thermoelectrics.caltech.edu
Patrik Čermák
E-mail: [email protected]