Thermoelectric properties of Yb_xCo₄Sb₁₂prepared under high pressure

Abstract

We report the thermoelectric properties of partially filled skutterudites Yb x Co 4 Sb 12 ð0 x 0:8Þ synthesized under high pressure. The phase compositions and actual Yb filling ratios were characterized by X-ray diffraction and electron probe microanalysis (EPMA), respectively. The EPMA results show that the maximum actual Yb doping content can be increased to 0.29, the highest for any Yb x Co 4 Sb 12 reported so far. The lattice thermal conductivity is reduced by increasing the Yb filling fraction. The minimum value is 2.02 W m %1 K %1 for Yb 0.6 Co 4 Sb 12 at 300 K. The electrical conductivity and the Seebeck coefficient for Yb-doped samples exhibit the typical behavior of n-type filled skutterudites. The maximum ZT value is 0.1 for Yb 0.2 Co 4 Sb 12 at room temperature.

Electrical and thermal transport properties of Y bxCo4Sb12 filled skutterudites with ultrahigh carrier concentrations

“…10,11 Such tendency can be more clearly reflected in Figure 6(b), which plots the relationship between the actual Yb filling fraction and PF by summarizing the published data of the Yb x Co 4 Sb 12 system at 300 K and 800 K, respectively. [18][19][20][21] With the increasing Yb filling fraction, the PFs at both 300 K and 800 K quickly increase. When the Yb content is around 0.21∼0.26, corresponding to a carrier concentration around 5∼6 × 10 20 cm −3 , they reach a maximum value (around 54 µW/cmK 2 ) at 800 K. Then, thePFs start to decrease as Yb filling fraction increases.…”

“…Therefore, as a promising TE material, the Yb-filled CoSb 3 system has been extensively studied since it was first reported in 2000. [14][15][16][17][18][19][20][21][22] Apart from single-filled skutterudites, Yb has been also used being the filling elements for the double-filled or multiple-filled skutterudites, which possesses higher TE performances. [23][24][25] For example, the maximum TE figure of merit (zT) of 1.7 and 2.0, have been reported for (Ba, La, Yb) x Co 4 Sb 12 and (Sr, Ba, Yb) x Co 4 Sb 12 , respectively.…”

“…However, although there has been numerous studies which relates to the Yb x Co 4 Sb 12 system, the maximum n value reported so far is only around 6 × 10 20 cm −3 because the real Yb filling fraction in CoSb 3 is limited around 0.20. [14][15][16][17][18][19][20][21][22] The lack of electrical and thermal transport properties for the Yb x Co 4 Sb 12 samples under higher carrier concentrations makes correlating optimal n value with the highest TE performance still unclear. Addressing this issue, the Yb x Co 4 Sb 12 samples with larger filling fractions are required.…”

The structural, transport, and magnetic properties of Yb-filled skutterudites YbyFexCo4−xSb12 synthesized under high pressure

“…8 The maximum Fe-substitution content of 1 was adopted because this Fe-substitution content already led to a transformation from n-type to p-type semiconductor. 15 Fe substituted Yb y Fe x Co 4-x Sb 12 samples with y ¼ 0.6, x ¼ 0, 0.2-1 were synthesized using a cubic-anvil high-pressure apparatus.…”

“…29 ). 8 The j L shows a minimum but its electronic properties are adversely affected by the high carrier concentration in Yb 0.29 Co 4 Sb 12 . To further optimize the TE performance, the excess electrons in Yb 0.29 Co 4 Sb 12 can be compensated by introducing a hole donor element in the Co site.…”