Electronic structure of thallium filled skutterudites studied by x-ray absorption and Mössbauer spectroscopy

Thallium LIII-edge x-ray absorption and iron-57 and tin-119 Mössbauer spectral measurements have been carried out to probe the electronic structure of the three sites in the filled skutterudite TlxCo4−yFeySb12 and TlxCo4Sb12−zSnz compounds with a range of x, y, and z values. The thallium LIII-edge x-ray absorption spectra are independent of x, y, and z and are well reproduced by full multiple scattering calculations with a cluster with a radius of 8.5 Å centered on thallium. The iron-57 Mössbauer spectra consist of two doublets and the major component is assigned to iron on the cobalt sublattice in view of its hyperfine parameters. The origin of the minor component is uncertain and is tentatively assigned to either iron with thallium vacancies as next nearest neighbors or to iron in the voids. The tin-119 Mössbauer spectral hyperfine parameters clearly indicate that tin substitutes for antimony in the skutterudite structure. Further, the tin electronic configuration is very similar to that of antimony and is insensitive to the thallium content.