High-Temperature Thermoelectric Properties of Co4Sb12-Based Skutterudites with Multiple Filler Atoms: Ce0.1In x Yb y Co4Sb12

Abstract

Void-filling in the CoSb 3 skutterudite lattice with different kinds of heavy elements has proven to be an effective mechanism to enhance thermoelectric performance due primarily to a reduction in lattice thermal conductivity. Specifically, our findings on the series In x Yb y Co 4 Sb 12 [0 £ (x, y) £ 0.2] have further motivated an attempt to form triple-filled skutterudites Ce 0.1 In x Yb yCo 4 Sb 12 with In and Yb concentrations [0 £ (x, y) £ 0.2] and with the Ce concentration held constant (Ce 0.1 ). All of these samples have been prepared via a simplified melting-annealing-sintering procedure and were first characterized by means of x-ray powder diffraction and scanning electron microscopy, followed by measurements of the Hall coefficient, electrical and thermal conductivities, and Seebeck coefficient. Our aim is to further elucidate the roles of the three elements (Ce, In, and Yb) in these materials. Compared with the addition of just In or Yb, we found that simultaneous addition of both In and Yb reduced the lattice thermal conductivity without significantly degrading the power factor. Further addition of the third element (Ce), along with In and Yb, also produced a similar result. However, we noticed that some of the In and Yb were also observed in the form of secondary phases (InSb and Yb 2 O 3 ), not entering entirely as filler atoms. As a result of our investigation, several compositions achieved increased sustainability and enhanced thermoelectric performance, with maximum ZT values of about 1.3 to 1.4 obtained at around 800 K.

Novel K rattling: A new route to thermoelectric materials?

“…16 Even further reductions have been reported in multi-filled compounds where two or more elements are used as rattler atoms. 7,[17][18][19][20][21][22][23][24] The larger reductions in the thermal conductivity in the thermal conductivity of multi-compared to single-filled materials is attributed to the scattering of a broader range of host lattice phonon frequencies due to the rattlers of the different elements vibrating at different frequencies. In a recent contribution 25 on the study of rattling in the Al-doped β-pyrochlores, AAl0.33W1.67O6 (A = K, Rb, Cs), we reported the discovery of novel rattling of K atoms in KAl0.33W1.67O6 involving both vibrations at a broad range of frequencies as well as local diffusion.…”

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

“…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. 7) and in In x Ce y Co 4 Sb 12 with solubility limit of In less than x ¼ 0.15.…”

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

“…A series of In-filled skutterudites of various groups prepared with various methods followed and confirmed that indium was useful as a filler. These investigations were extended to double-filled skutterudites of In with Sn [29], with Ba [3,16,[30][31][32][33][34][35][36][37], with Tl [38], with Pb [35], with Ce [6,[39][40][41][42], with Pr [27], with Nd [21,43], with Yb [7,8,16,19,[44][45][46][47][48][49], with Lu [50], and to triple filled skutterudites of In with Ba and Ce [51], with Ba and Yb [16,52], with La and Yb [47], with Ce and Yb [41,42,53] and Ga and Tl [26]. There are also attempts to improve the TE properties by doping and/or alloying e.g.…”