Tellurium-based Nanocomposites as Thermoelectric Materials

Kurzfassung

Thermoelectric materials which are based on tellurium have been proven to be very effective for the medium temperature range. For example doping of lead telluride with silver-antimony-telluride lead to a ZT value of 2.2 at 800 K for the bulk.1 This extraordinary thermoelectric performance can be attributed mainly to the strongly reduced thermal conductivity due to the formation of Ag-Sb-nanodots which are embedded into the matrix and so do not affect the electrical conductivity.2 To understand the microstructure and the importance of the minority phase in this complex system and their influences on the thermoelectric properties various synthetic approaches are of great interest. In this work we applied a simple ball milling method to synthesize nanocomposites on the basis of a group-IV-telluride with different amounts of a dopand. Three compacting methods for those nanopowders such as cold pressing / annealing, hot pressing and short-term-sintering were compared regarding the density of the obtained pellets. The samples were characterized via x-ray diffraction patterns to analyze the phase composition and measuring the thermoelectric transport properties such as thermal conductivity, electrical conductivity and Seebeck coefficient. A TEM-study including EDX-measurements and electron-diffraction was performed to reveal form, size and agglomeration of the nanoparticles and the local distribution of the constituting elements. [1] K.-F. Hsu, S. Loo, F. Guo, W. Chen, J. S. Dyck, C. Uher, T. Hogan, E. K. Polychroniadis, M. G. Kanatzidis, Science 2004, 303, 818 - 821. [2] E. Quarez, K.-F. Hsu, R. Pcionek, N. Frangis, E. K. Polychroniadis, M. G. Kanatzidis, J. Am. Chem. Soc. 2005, 127, 9177 - 9190.