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High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)

“…For all RFe 4 Sb 12 samples, lattice constant a increases with increasing r ion . r, S and j for all samples are measured in the temperature range from 300 to 800 K. Since 12 , and YbFe 4 Sb 12 at 750 K. All samples possess low j L due to the "rattling" effect of the fillers, which could scatter lowfrequency heat carrying phonons. For RFe 4 Sb 12 with trivalent fillers (R ¼ La, Ce, Pr, and Nd), the slight increase of j L above 700 K can be explained by the bipolar diffusion caused by the intrinsic excitation, which is not observed in RFe 4 Sb 12 with divalent fillers (R ¼ Ca, Sr, Ba, Eu, and Yb).…”

“…In filled skutterudites, based on the assumption that the effect of the additional j L reduction by the fillers is a localized behavior, 48 total lattice thermal resistivity 12 ] framework, W PD is the thermal resistivity contributed by point defect, and W R is the thermal resistivity contributed by resonant scattering due to the local rattling of guest fillers, respectively. In principle, W PD includes the effect of structure strain (W S ) and mass fluctuation (W M ) between the void and filler.…”

“…50 Thus, for a resonant scattering, W R is almost in proportion to 1/(Dr), 3 where Dr is the distance between the positive charge of filler ion and the negative charge of its nearest Sb anion, and thus equal to (r cage À r ion ). Here, r cage is the Sb-icosahedron void radius in RFe 4 Sb 12 and an average value of 1.94 Å is used in this paper. 1 Figure 7 shows W L at 300 K as a function of (r cage À r ion ) for RFe 4 respectively.…”

“…1 The general structure formula of filled skutterudites is R y M 4 Sb 12 , where R can be alkaline, alkaline-earth, lanthanide, or actinide metals, y is the filling fraction, and M is Fe, Ru, Os, Co, Rh, or Ir. Investigation on the thermoelectric properties in filled skutterudites has been initially started in 1990s.…”

“…[2][3][4][5][6][7][8][9][10] Earlier studies are mainly focused on p-type Fe x Co 4Àx Sb 12 -based compounds and the values of the dimensionless thermoelectric figure of merit (ZT) had been reported above unity. 5,6,9,11,12 The progress in n-type filled skutterudites was rather slowly until partially filled skutterudites R y Co 4 Sb 12 with high filling fraction of the fillers were synthesized and reported with good thermoelectric performance at elevated temperature. 13,14 After that, improving the thermoelectric figure of merit in ntype skutterudites gained keen interest in the next decade.…”