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Avoided crossing of rattler modes in thermoelectric materials

Jakob Andreasson (Institutionen för teknisk fysik, Kondenserade materiens fysik)
Nature materials Vol. 7 (2008), p. 811-815.
[Artikel, refereegranskad vetenskaplig]

Engineering of materials with specific physical properties has recently focused on the effect of nano-sized ‘guest domains’ in a ‘host matrix’ that enable tuning of electrical, mechanical, photo-optical or thermal properties. A low thermal conductivity is a prerequisite for obtaining effective thermoelectric materials, and the challenge is to limit the conduction of heat by phonons, without simultaneously reducing the charge transport. This is named the ‘phonon glass–electron crystal’ concept and may be realized in host–guest systems. The guest entities are believed to have independent oscillations, so-called rattlermodes,which scatter the acoustic phonons and reduce the thermal conductivity. We have investigated the phonon dispersion relation in the phonon glass–electron crystal material Ba8Ga16Ge30 using neutron triple-axis spectroscopy. The results disclose unambiguously the theoretically predicted avoided crossing of the rattler modes and the acoustic-phonon branches. The observed phonon lifetimes are longer than expected, and a new explanation for the low L is provided.



Denna post skapades 2008-12-11. Senast ändrad 2009-03-04.
CPL Pubid: 81114

 

Institutioner (Chalmers)

Institutionen för teknisk fysik, Kondenserade materiens fysik (1900-2015)

Ämnesområden

Fysik

Chalmers infrastruktur