Rattling motion of a guest ion in type-I clathrate compounds has been studied by Raman scattering measurements. The anomalous energy-decrease of guest atom vibration has been observed for Sr8Ga16Si 30-xGex and Ba8Ga16Si 30-xGex as well as A8Ga16Ge 30 with decreasing temperature. This result shows that the 4th order anharmonic potential is also important for the guest-ion motion of Sr- and Ba-clathrates. The energy of the guest mode observed by the Raman scattering is consistent with the Einstein temperature estimated by the specific heat measurements. It is confirmed that the off-center rattling plays an important role to suppress the lattice thermal conductivity.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)