Vibrational dynamics of the type-I clathrateBa8ZnxGe46−x−y◻

Phononic filter effect of rattling phonons in the thermoelectric clathrate Ba8Ge40+xNiEuchner1, Pailhés2, Nguyen3 et al. 2012Phys. Rev. B909630View full textAdd to dashboardCite

“…Since the linewidth of these peaks is larger than the energy resolution, several phonon branches can be contained in a peak. Later, the peaks E 1 and E 2 will be identified as stemming from localized Ba motions in the large Ba(Ge,Ni) 24 cages, while the peak E 3 contains both optical phonon modes from the (Ge,Ni) 46 host framework and guest phonon modes, in agreement with previous INS [5, 6, 9, 26, 27], Raman [28] and theoretical [9,25] reports. In a next step the TA phonon branch was investigated by performing energy scans around the Bragg peak (600) for a set of reduced phonon wave vectors, q = (0kk), covering an entire BZ (0 ≤ k ≤ 1).…”

Phonon engineering through crystal chemistry

“…81,[85][86][87] The ability to predict the frequency of the rattler mode for different guest species is a particularly attractive feature of this work, helping to guide development of skutterudites with multiple guest elements. 88 Despite the vast body of research concerning rattling modes, there is an ongoing debate in the community: Is resonant scattering or a local reduction in n g near the avoided crossing the dominant cause of low k L ?…”

“…67,[79][80][81][82][83] The flatness of the guest mode can be deduced from the width of the heat capacity or phonon DOS peak. For example, in the germanium-clathrates, broad peaks observed in the phonon DOS reveal strong coupling between the guest and host modes.…”

Crystal structure and thermoelectric properties of KxBa8−xZnyGe46−y clathrates

“…1). [18][19][20][21][22][23][24][25][26] 13 where the observed increases in mobility were mainly as a result of a decrease in the number of substituting atoms. Johnsen et al characterized several Ba 8 Ni 6Àx Ge 40þx (0 x 0.6) samples.…”

“…Melnychenko-Koblyuk et al and Koza et al prepared ternary Ba-Zn-Ge clathrates. 21,24 The Ba 8 Zn x Ge y (0 x 6) samples contained vacancies in their frameworks, which probably scattered carrier electrons and reduced carrier mobility. On the other hand, Nasir et al prepared vacancy-free quaternary clathrates Ba 8 (Zn,Cu) 6 Ge 40 and Ba 8 (Zn,Pd) 6 Ge 40 , whose 6c sites were occupied almost solely by Zn and Cu or Pd atoms; unfortunately, these clathrates are not reported to have high ZT values.…”