Our Working Group “Methods for Characterization of Transport Phenomena in Energy Materials” (EM-AMCT) focuses on basic aspects in the research on thermoelectric materials, well prior to device fabrication. It seeks a fundamental understanding of the structure-functionality relation and, in particular, of the dynamic interplay of charge and quasi-particle transport as necessary prerequisite for optimizing design strategies for novel thermoelectric materials. Insights in the interaction processes on the level of elementary excitations in the solid state is considered as key to designing macroscopic transport properties.
The Working Group operates laboratories and X-ray and neutron scattering instruments at HZB’s Lise-Meitner-Campus in Berlin Wannsee and HZB’s Wilhelm-Conrad-Röntgen-Campus in Berlin Adlershof as vital and invaluable parts of its research activities.
The following list gives an overview of the infrastructure operated by the Working Group. For further detailed information we invite the visitors of our webpage to use the links below.
- Laboratory for Thermoelectric Materials Development: Spark-plasma-sintering equipment allows the synthesis of nanostructured bulk TE materials. A Potential-Seebeck-microprobe apparatus and equipment for simultaneously measuring electrical conductivity and Seebeck coefficient as well as in-house developments of 3ω-instrumentation are assets for thermoelectric characterization of novel materials and the rapid evaluation of the merits of alternative synthesis routes.
- Laboratory for Thermoelectric Transport Measurements: A complete instrument suite for thermoelectric transport measurements on novel materials is available. The laboratory includes a Laser Flash Apparatus, Hall measurement equipment, Differential Scanning Calorimetry equipment and a dilatometer.
- FLEXX: The cold-neutron triple axis spectrometer with its innovative multi-energy analyzer option MultiFLEXX and the neutron resonance spin-echo (NRSE) option at BER II provides highest energy resolution and allows for lifetime studies on quasi-particles in solid state samples. Systematic methodological developments of the NRSE spectroscopy applied to single-crystalline materials in recent years [1-5] are now the basis to fundamentally link macroscopic transport in TE to the quasi-particle dispersion and lifetime as part of the Working Group’s scientific mission.
- PEAXIS: The new end-station at BESSY II offers capabilities for resonant inelastic X-ray scattering (RIXS) and angular resolved photoemission spectroscopy (ARPES) measurements. Wavevector-resolved RIXS allows in particular accessing electronic states and their coupling to dispersive excitations in energy materials.
Research activities within EM-AMCT focus currently on three TE material classes:
In all of these materials, the thermal conductivity is lowered by the suppression of phonon propagation by providing additional phonon Umklapp scattering either by introducing additional filler atoms, as for the skutterudites, or by interfaces, as for mesoporous silicon.
Research on thermoelectric materials offers a variety of fascinating scientific questions to be studied. We encourage highly motivated students who are interested in broadening their background in experimental condensed matter physics and in developing their scientific skills to apply for a Bachelor’s thesis project or a Master’s thesis project. Please contact PD Dr. Klaus Habicht (email@example.com) if you are interested.
 K. Habicht, R. Golub, F. Mezei, B. Keimer, T. Keller. Temperature-dependent phonon lifetimes in lead investigated with neutron-resonance spin-echo spectroscopy. Phys. Rev. B 69 104301 (2004).
 K. Habicht, R. Golub, T. Keller. The resolution function in neutron spin-echo spectroscopy with three-axis spectrometers. J. Appl. Cryst. 36, 1307 (2003).
 F. Groitl, K. Kiefer, and K. Habicht. A resolution model for mode multiplets probed with neutron resonance spin-echo spectroscopy. Physica B 406, 2342 (2011).
 P. Aynajian, T. Keller, S.M. Shapiro, L. Boeri, K. Habicht, B. Keimer. Energy gaps and Kohn anomalies in elemental superconductors. Science 319, 1509 (2008).
 T. Keller, P. Aynajian, K. Habicht, L. Boeri, S. K. Bose, B. Keimer. Momentum-resolved electron-phonon interaction in lead determined by neutron resonance spin-echo spectroscopy. Phys. Rev. Lett. 96, 225501 (2006).
 K. Lieutenant, T. Hofmann, C. Schulz, M. V. Yablonskikh, K. Habicht, and E. F. Aziz. Design concept of the high-resolution end-station PEAXIS at BESSY II: Wide-Q-range RIXS and XPS measurements on solids, solutions, and interfaces. Journal of Electron Spectroscopy and Related Phenomena, 210:54–65, 7 2016.
 K. Lieutenant, T. Hofmann, C. Zendler, C. Schulz, E. F. Aziz, and K. Habicht. Numerical optimization of a RIXS spectrometer using raytracing simulations. Journal of Physics: Conference Series, 738(1):012104, 2016.