Prospective Thermoelectric Prospective Thermoelectric TelluridesTellurides

Patrik ČermákPatrik ČermákUniversity of Pardubice, Czech Republic

E2.1.8x6761

„„Thermoelectrics as an Thermoelectrics as an ‘‘energy gateenergy gate’’ to deep space“ to deep space“

Space probes (e.g.):

• Voyager 1, 2 (1977)

• Galileo (1989)

• Ulysses (1990)

• Cassiny (1997)

• New Horizons (2006)

I. Introduction to ThermoelectricsI. Introduction to Thermoelectrics

1. Seebeck effect 2. Peltier effect

Thermoelectric materials

• The main aim of researching of TE materials in general is enhance their efficiency in defined temperature range.

p-type n-type

U+ -

+++

---

Heating

Performance criterion for practical applications:

T

ZT2

TU ABAB TIQ

p-type n-type+++

---

- --

Cooling

Q

500 1000 15000

1

2

3

4

p - SiGe

ZT = 1

n - SiGe

p - Bi0.5

Sb1.5

Te3

n - PbTe

n - Bi2Te

2.95Se

0.05

Z*1

03 (K

-1 )

T ( K )

p - Ce Fe0.9

Co0.1

Sb3

p - Zn4Sb

3

500 1000 15000

1

2

3

4

p - SiGe

ZT = 1

n - SiGe

p - Bi0.5

Sb1.5

Te3

n - PbTe

n - Bi2Te

2.95Se

0.05

Z*1

03 (K

-1 )

T ( K )

p - Ce Fe0.9

Co0.1

Sb3

p - Zn4Sb

3

II. ResearchII. Research

Motivation

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).

2. Preparation of „novel TE material – GaGeTe“ with enhanced electrical conductivity (focuse on figure of merit ZT) and development of complementary n-type.

Characterization

• X-ray Diffraction

• Seebeck coefficient (Tc)

• Electrical conductivity c

• Thermal conductivity

• Hall coefficient RH (B║c)

Bi2Te3

c

a

Sb

Sb

Te 1

Te 1

Te 2

Te 2

Sb

Te 1

Te 1

Sb

Te 1

Bi

Bi

Bi

Bi

c

a

Sb

Sb

Te 1

Te 1

Te 2

Te 2

Sb

Te 1

Te 1

Sb

Te 1

Bi

Bi

Bi

Bi

GaGeTe

III. ResultsIII. Results

Bi2+xTe3-x-y-zSeyIz

430 K

GaGeTe1-xIx

50 100 150 200 250 300 350 400 450

60

80

100

120

140

160

180

200

220

240

260

280

GaGeTe (no tempering) Bi

0,5Sb

1,5Te

2,9Se

0,1

(

V/K

)

T (K)

IV. DiscussionIV. 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+xTe3-x-y-zSeyIz:

n

GaGeTe1-xIx

This (ternary) system show high Seebeck coefficient then the state-of-the-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.

T

n

V. ConclusionsV. 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 .

Now will follows the measurements of the other TE properties including „certainty“ identifications by XRD.

TeV

TeV

TeV

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 attentionThank you for your attention

References for this presentationReferences 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: patrik.cermak@email.cz