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Thermoelectric Material Synthesis - From Nanoparticles to Epitaxial Thin Films

The development of efficient thermoelectric generators TEG and thermoelectric coolers have attracted considerable attention in recent years. Radioisotope thermoelectric generators (RTG) are known since the 1950´s, but their low thermoelectric efficiency as given by the dimensionless figure of merit ZT= (α2σ/λ)T (α = Seebeck coefficient, σ = specific electrical conductivity, λ = thermal conductivity = sum of electronic λel and lattice λla contribution, T = absolute temperature [K]) inhibited their broad technical application. Nanostructuring has been proven to be a promising method for increasing the thermoelectric efficiency (zT) of a given material due to an efficient phonon scattering at boundaries and interfaces, resulting in a decreased thermal conductivity, and a simultaneously increased Seebeck coefficient due to both quantum confinement effects and the modification of the electronic band structure.

We will report on the synthesis of tetradymite-type - Sb2Te3, Bi2Te3, (BixSb1−x)2Te3 - nanoparticles[1] and thin films[2] by use of different solution-based and gas phase-based processes as well as on their thermoelectric properties. The role of the synthesis pathway, material composition and material processing of the resulting properties is discussed.

[1] J. Schaumann, M. Loor, D. Ünal, A. Mudring, S. Heimann, U. Hagemann, S. Schulz, F. Maculewicz, G. Schierning, Improving the zT value of thermoelectrics by nanostructuring: Tuning the nanoparticle morphology of Sb2Te3 by ionic liquids, Dalton Trans. 46, 656 (2017).

[2] G. Bendt, K. Kaiser, A. Heckel, F. Rieger, D. Oing, A. Lorke, N. Perez Rodriguez, G. Schierning, C. Jooss, S. Schulz, Structural and thermoelectrical characterization of epitaxial Sb2Te3 high quality thin films grown by thermal evaporation, Semicond. Sci. Technol. 33, 105002 (2018).

[3] F. Rieger, K. Kaiser, G. Bendt, V. Roddatis, S. Schulz, C. Jooss, Low intrinsic c-axis thermal conductivity in PVD grown epitaxial Sb2Te3 films, J. Appl. Phys. 123, 175108 (2018).

Prof. Dr. Stephan Schulz
University of Duisburg-Essen
Additional Authors:
  • Dr. Georg Bendt
    Universität Duisburg-Essen
  • Sarah Salloum
    Universität Duisburg-Essen
  • Kevin Kaiser
    Universität Duisburg-Essen


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