When does a crystal conduct heat like a glass?

Abstract

Semiconducting crystalline materials that are poor conductors of heat are important as thermoelectric materials and for technological applications involving thermal management.

Rattling guest atoms in Si, Ge, and Sn‐based type‐II clathrate materials

“…The low thermal conductivity measured in these compounds is due to the weak guest-host electronic interactions, which leads to strong coupling between the localized guest rattler vibrations and the host acoustic modes. This interpretation is consistent with transport [11][12][13][14][15][16][17][18], Raman scattering [19] and acoustic measurements [20,21] as well as with theoretical calculations [22,23]. Several theoretical studies of the electronic, structural, and vibrational properties of both the pure Type I clathrate materials and various compounds based on the Type I lattice structure have also been carried out [24][25][26][27][28][29][30][31][32][33].…”

Low-temperature heat capacity ofSr8Ga16Ge30andXu1, Tang2, Sato3 et al. 2010Phys. Rev. B

“…3,4 Quantum tunneling of guest atoms has been a very important issue to understand the physical properties of clathrates. [5][6][7][8][9][10] For Eu clathrates, quantum tunneling at ϳ450 MHz frequency among the four equivalent sites was discussed from the viewpoint of Mössbauer experiments. 5 The mixed state of thermal rattling and tunneling are argued using raman spectroscopy in the Ge clathrate family.…”

Maximum entropy method analysis of thermal motion and disorder in thermoelectric clathrate Ba8Ga16Si30

“…[10][11][12][13][14][15] In this respect well-tested models of thermal vibrations and lattice dynamics in solids have had a remarkable comeback. 16,17 By applying the Debye model, Sales and co-workers have shown that even the most basic crystallographic parameter, the average isotropic mean square displacement parameter (͗U 2 ͘) for the framework atoms, can provide a quite accurate estimate of the thermal conductivity.…”