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

• Published in: arXiv.org
• Main Authors: de Abrantes, Juliana G, Cantarino, Marli R, Wagner R da Silva Neto, Freire, Victória V, Figueiredo, Alvaro G, Germano, Tarsis M, Mounssef, Bassim, Bittar, Eduardo M, Leithe-Jasper, Andreas, Garcia, Fernando A
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 15.08.2022
• Subjects: Barium; Bulk modulus; Calcium; Compressibility; Debye-Waller factor; Elastic properties; Experiments; Fine structure; Oscillators; Pressure dependence; Sodium; Strontium; Temperature dependence; X ray absorption; X-ray diffraction
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2203.14821

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.