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A6: Characterization

Direct Measurement of Thermal Displacement of Atoms in Thermoelectric Materials and its Nature in Phonon Scattering*

Lijun Wu, Yimei Zhu, and Qiang Li
Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973

Measurement of local disorder and thermal vibrations is important for understanding the underlying mechanisms of the reduced thermal conductivity in thermoelectric materials. Recently, we showed that thermal and static displacement in the layered thermoelectric Ca3Co4O9 can be determined accurately by simultaneous acquisition of high-angle- and mediate-angle- annular dark field images in scanning transmission electron microscopy (STEM).1 In this presentation, we will present a few more case studies on the application of this technique to several well-known high performance thermoelectric materials. Unlike diffraction analysis that derives the overall displacements in the crystal from the intensities of Bragg reflections, we directly measure the atomic displacement in real space, thereby enabling us to refine independently the atomic displacement of various constitute atoms in a compound that is crucial to revealing their different nature in phonon scattering.

References

[1] L. Wu, Q. Meng, Ch. Jooss, Jin-Cheng Zheng, H. Inada, D. Su, Q. Li, and Y. Zhu, Adv. Func. Mat. (2014).

*The work is support by the U.S. DOE, under contract No.DE-AC02-98CH10886.