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 Seebeck effect 2. Peltier effect p-type n-type U + - Heating p-type n-type + - Cooling Q Thermoelectric materials The main aim of researching of TE materials in general is enhance their efficiency in defined temperature range. Performance criterion for practical applications:

II. Research Motivation Bi2Te3 Characterization GaGeTe 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). Preparation of „novel TE material – GaGeTe“ with enhanced electrical conductivity s (focuse on figure of merit ZT) and development of complementary n-type. Bi2Te3 Characterization X-ray Diffraction Seebeck coefficient a (Tc) Electrical conductivity sc Thermal conductivity k Hall coefficient RH (B║c) GaGeTe

III. Results Bi2+xTe3-x-y-zSeyIz GaGeTe1-xIx 430 K

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: T a n Substitution of „Te“ for „I“ - Bi2+xTe3-x-y-zSeyIz: n s a a 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.

V. Conclusions Bi2+xTe3-x-y-zSeyIz GaGeTe1-xIx 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. 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).

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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: patrik.cermak@email.cz