Raman spectroscopy investigation of lanthanide-filled and unfilled skutterudites

Raman-scattering spectra at room temperature and 10 K are studied for binary “unfilled” and lanthanide-filled skutterudite antimonides. In the binary skutterudites ${\mathrm{IrSb}}_3$ and ${\mathrm{RhSb}}_3$ all eight Raman-active vibrational modes have been identified while seven of the eight modes have been identified in ${\mathrm{CoSb}}_3.$ In the case of the filled skutterudites these vibrational modes are sensitive to the lanthanide “filler” ions which produce a shift and large broadening of the vibrational modes. Polarization measurements on these polycrystalline samples were used to identify the $A_g$ modes. The experimental data are compared to theoretical predictions.