We report the thermal conductivity κ and specific heat C measurements down to 0.3K on single-crystalline samples of n-type Sr8Ga 16Ge30 and p-type Ba8Ga16Ge 30 clathrates. The overall temperature dependence of κ(T) of both samples with a plateau at about 20K and a quadratic T dependence below 1K is well described by the soft-potential model. Using the soft-potential parameter of 4.4K derived from the analysis of κ(T) for Sr 8Ga16Ge30, the broad maximum of C/T3 centered at 7K is also well reproduced. The density of states of quasilocalized vibrational modes for Sr atoms in Sr8Ga16Ge30 has a maximum at 0.7 THz, in agreement with the low-energy peak in a previous Raman scattering study.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)