Thermoelectric Properties of Co4Sb12 Skutterudite Materials with Partial In Filling and Excess In Additions

Abstract

The properties of Co 4 Sb 12 with various In additions were studied. X-ray diffraction revealed the presence of the pure d-phase of In 0.16 Co 4 Sb 12 , whereas impurity phases (c-CoSb 2 and InSb) appeared for x = 0.25, 0.40, 0.80, and 1.20. The homogeneity and morphology of the samples were observed by Seebeck microprobe and scanning electron microscopy, respectively. All the quenched ingots from which the studied samples were cut were inhomogeneous in the axial direction. The temperature dependence of the Seebeck coefficient (S), electrical conductivity (r), and thermal conductivity (j) was measured from room temperature up to 673 K. The Seebeck coefficient of all In-added Co 4 Sb 12 materials was negative. When the filler concentration increases, the Seebeck coefficient decreases. The samples with In additions above the filling limit (x = 0.22) show an even lower Seebeck coefficient due to the formation of secondary phases: InSb and CoSb 2 . The temperature variation of the electrical conductivity is semiconductor-like. The thermal conductivity of all the samples decreases with temperature. The central region of the In 0.4 Co 4 Sb 12 ingot shows the lowest thermal conductivity, probably due to the combined effect of (a) rattling due to maximum filling and (b) the presence of a small amount of fine-dispersed secondary phases at the grain boundaries. Thus, regardless of the non-single-phase morphology, a promising ZT (S 2 rT/j) value of 0.96 at 673 K has been obtained with an In addition above the filling limit.

In-doped multifilled n-type skutterudites with ZT= 1.8

“…8a shows the change of the Lorenz number with temperature, calculated with Eqs. (3)- (5). The slope for all skutterudites does not vary much, however, the values are the closer to each other at higher temperatures.…”

Neutron diffraction and thermoelectric properties of indium filled InxCo4Sb12 (x = 0.05, 0.2) and indium cerium filled Ce0.05In0.1Co4Sb12 skutterudites

“…Because the expansion of the lattice parameter of the skutterudite phase indicates the filling fraction of the skutterudite composition, the stoichiometry of the three samples can be calculated accordingly. As basis, the reported data from He et al and Mallik et al are used. Grytsiv et al suggested a linear regression as follows: …”

“…This filling of the crystal structure has a significant influence on the macroscopic transport properties. In particular, indium as filler element was reported in many publications due to the high ZT and has recently also gained attraction because of a complex doping behavior in the skutterudite structure .…”

From Occupied Voids to Nanoprecipitates: Synthesis of Skutterudite Nanocomposites in situ

“…Moreover, they often exhibit good structural properties13,24 and low coefficients of thermal expansion 25–27. In addition, research focused on indium‐filled skutterudites revealed that many samples contain ZT‐enhancing InSb nanoinclusions formed in situ 28–31. However, the source of indium has not yet been adequately established.…”