Raman spectroscopy investigation of partially filled skutterudite

Raman-scattering spectra for partially filled skutterudite LaxFe3CoSb12 (x=0.2, 0.4, 0.6, and 0.8) at room temperature have been obtained. Six of nine modes in the partially filled skutterudites, LaxFe3CoSb12 (x=0.2, 0.4, 0.6, 0.8), including the two Ag modes were identified. The lanthanum ions filling the voids cause a broadening of vibrational mode of the Sb4 ring vibration mode in skutterudite. However, the degree of broadening decreases with the increase of the filling ratio. It can be concluded that the degree of `rattlingʹ decreases with the increase in the filling ratio. The filling atoms make the Raman intensity of the stretching vibrational mode of the shorter Sb–Sb bond decrease a little, but enhance the lower energy mode intensity a lot, which is the stretching of the long Sb–Sb bond.