Synthesis, crystal structure, and transport properties of Fe substituted rhombohedral skutterudite derivatives Co4−xFexGe6Se6

• Co4−xFexGe6Se6 compositions crystallize in a rhombohedral symmetry.
• Fe substitution in Co4Ge6Se6 can significantly affect the transport properties.
• Tuning of the transport properties is possible in these compositions.

We report on the synthesis and low temperature transport properties of rhombohedral derivatives of the cubic skutterudite CoSb3, namely Co4−xFexGe6Se6 with x = 0, 1, 1.5. Rietveld refinement and elemental analyses were used to identify the structure and stoichiometry of the compositions. The thermal conductivity was investigated by employing the Debye model with different phonon-scattering parameters. This investigation demonstrates that Fe substitution is feasible in these skutterudite derivatives and can significantly affect the transport properties as compared with Co4Ge6Se6.