Thermoelectric Properties of Indium-Filled Skutterudites

Abstract

Structural, electrical, and thermal transport properties of CoSb3 partially filled with indium are reported. Polycrystalline samples of In x Co4Sb12 (0 ≤ x ≤ 0.3) were prepared by solid-state reaction under a gas mixture of 5% H2 and 95% Ar. The solubility limit of the indium filling voids in CoSb3 was found to be close to 0.22. Synchrotron X-ray diffraction refinement of the x = 0.2 sample showed that the indium is located in the classic rattler site and has a substantially larger thermal factor than those of Co and Sb. The electrical resistivity, Seebeck coefficients, and thermal conductivity of the In x Co4Sb12 samples were measured in the temperature range of 300−600 K. All samples showed metal-like behavior, and the large negative Seebeck coefficients indicated n-type conduction. The thermal conductivity decreased with increasing temperature for all samples. A thermoelectric figure-of-merit (ZT) ≥ 1 (n-type) has been achieved when x ≥ 0.2 in In x Co4Sb12 at 575 K.

Phase diagram of In–Co–Sb system and thermoelectric properties of In-containing skutterudites

“…Experimentally, a lling limit of In was rst reported to be around x ¼ 0.22 in In-doped CoSb 3 by He et al 2 and later reproduced by Mallik. 6 In was also observed in the form of secondary phase InSb, and therefore assumed as not entering entirely as ller atoms in In x Yb y Co 4 Sb 12 with solubility limit of In less than x ¼ 0.20 (ref.…”

“…7b the S-n dependence in indium-containing complex compound defect samples follows the extrapolated curve of normal lled skutterudites 2,5,[21][22][23][24][25][26][27][28] . Fig.…”

“…Among various kinds of lled skutterudite thermoelectric materials, Indoped skutterudites have attracted much attention. For single lling, zT was reported to achieve 1.2 for In 0.25 Co 4 Sb 12 at 575 K by He et al 2 For double lling, zT of 1.43 for In 0.2 Ce 0.15 Co 4 Sb 12 at 800 K was reported by Li et al 3 However, the nature of In incorporation has not yet been fully understood and there are several different mechanisms for enhancement of zT. One possible mechanism is that the In atom goes into the ller site and due to the rattling and avoided crossing effect, 4 the thermal conductivity becomes greatly decreased, and thus zT is enhanced; another possible mechanism is that doping of In results in a nanostructured InSb phase that is evenly distributed on the boundaries of the skutterudite phase, 3 which lowers thermal conductivity and enhances zT.…”

How thermoelectric properties of p-type Tl-filled skutterudites are improved

“…The unit cell contains two structural cages that can be filled by a variety of guest atoms such as rare earth elements, [4][5][6][7] alkaline earth metals, [8][9][10] alkali metals, 11,12 and group 13 elements. [13][14][15][16][17] When the guest atom denoted by R is incorporated into the cages, the general formula of the compounds, referred to as filled skutterudites, becomes RM 4 × 12 .…”

“…19 CoSb 3 -based skutterudites filled by group 13 elements, such as Ga, In, or Tl, have recently received attention in TE research due to their excellent TE performance. [13][14][15][16] Any filling atoms in CoSb 3 will form an n-type skutterudite since all fillers are stripped of electrons to a lesser or greater a Electronic mail: kurosaki@see.eng.osaka-u.ac.jp 2166-532X/2013/1(3)/032115/5 © Author(s) 2013 1, 032115-1 degree and these electrons go into the conduction band. However, for a powerful TE module, a similar performance in both n-and p-type TE materials is required.…”