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Jeudi 11 Décembre 2014, 14h
Amphi Howleck, Esc C, 1ème etage
Localization of propagative phonons in crystalline complex materials.
S. Pailhès
IMN, Lyonn
Low thermal conductivity is usually associated with highly disordered, aperiodic, nanostructured or even amorphous solids. However, certain materials conduct heat poorly in spite of a perfectly crystalline structure. Understanding the mechanism of this phenomenon is not only of fundamental interest but also highly relevant for the field of thermoelectric energy conversion. A thermoelectric material should combine low thermal conductivity with high electron mobility. A class of materials that has proven to perfectly meet the above requirement are intermetallic clathrates of which the type-I clathrate with a typical value of the thermal conductivity of about 1.5 W/mK at 300 K. It is a guest-host system in which alkaline earth metals fills large polyhedral cavities in a covalently bound, fully ordered Si/Ge framework .
In this talk, I will present experimental investigations and ab intio simulations of phonons in different clathrates which evidence how the acoustic waves interact with the guest atoms vibrations and how does it impact the heat transport in these materials.
S. Pailhès, "Localization of Propagative Phonons in a Perfectly Crystalline Solid", PRL Phys. Rev. Lett. 113, 025506 (2014)
H. euchner, S. Pailhès, "Phononic filter effect of rattling phonons in the thermoelectric clathrate Ba8Ge40+xNi6−x", Phys. Rev. B 86, 224303 (2012)