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arXiv · 2203.14821

Vibrational and structural properties of the $R$Fe$_{4}$Sb$_{12}$ ($R=$Na, K, Ca, Sr, Ba) filled skutterudites

Juliana G. de Abrantes·Marli R. Cantarino·Wagner R. da Silva Neto·Victória V. Freire·Alvaro G. Figueiredo·Tarsis M. Germano·Bassim Mounssef Jr.·Eduardo M. Bittar·Andreas Leithe-Jasper·Fernando A. Garcia
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Abstract

Vibrational and elastic properties of the $R$Fe$_{4}$Sb$_{12}$ skutterudites are investigated by, respectively, temperature $(T)$ dependent extended X-ray absorption fine structure (EXAFS) and pressure $(P)$ dependent x-ray diffraction (XRD) experiments. The Fe $K$-edge EXAFS experiments of the $R=$ K, Ca and Ba materials were performed in the $T$-interval $6<T<300$ K and XRD experiments of the $R=$ Na, K, Ca, Sr and Ba materials were performed in the $P$-interval $1\text{ atm }<P<16$ GPa. From EXAFS, we obtained the correlated Debye-Waller parameters that were thus analyzed to extract effective spring constants connected with the Fe-$Y$ (where $Y=$ either $R$, Fe or Sb) scattering paths. Our findings suggest that in the case of the light cations, $R=$ K or Ca, the $R$ atoms are relatively weakly coupled to the cage, in a scenario reminiscent to the Einstein oscillators. From the XRD experiments, we obtained the bulk modulus $B_{0}$ for all $R=$Na, K, Ca, Sr and Ba materials, with values ranging from $77$ GPa ($R=$ K) to $R=99$ GPa ($R=$ Ba) as well as the compressibility $\beta$ as a function of $P$. The trend in $\beta$ as a function of the $R$ filler is discussed and it is shown that it does not correlate with simple geometrical considerations but rather with the filler-cage bonding properties.

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Juliana G. de Abrantes, Marli R. Cantarino, Wagner R. da Silva Neto, Victória V. Freire, Alvaro G. Figueiredo, Tarsis M. Germano, Bassim Mounssef Jr., Eduardo M. Bittar, Andreas Leithe-Jasper, Fernando A. Garcia. 2022-03-28. Vibrational and structural properties of the $R$Fe$_{4}$Sb$_{12}$ ($R=$Na, K, Ca, Sr, Ba) filled skutterudites. https://doi.org/10.1103/physrevmaterials.6.085403

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