High-Pressure Synthesis and Thermoelectric Properties of Partially Filled Skutterudites R_xCo₄Sb₁₂ (R = In, Tb and Dy)

Abstract

Partially filled skutterudite compounds R_xCo₄Sb₁₂ (R = In, Tb and Dy, nominal composition 0.1 ≤ x ≤ 1.5) were synthesized under high pressure using multi-anvil presses. The samples were analyzed by x-ray diffraction and scanning electron microscopy (SEM) with energy-dispersive x-ray spectrometry (EDX). The highest actual filling fraction x of In, Tb and Dy are 0.64, 0.22 and 0.15, respectively. The electron back-scatter diffraction (EBSD) result indicates that the grain size of In_0.8Co₄Sb₁₂ is 2–5 µm. Electrical resistivity, Seebeck coefficient, and thermal conductivity were measured between 2 K and 300 K. The maximum value of the dimensionless figure of merit ZT is 0.10 for nominal composition In_0.8Co₄Sb₁₂ at 300 K. We studied guest ion R dependence of lattice thermal conductivity κ_L for R_xCo₄Sb₁₂ systematically based on a simple model for the rattling. The reduction rate of κ_L of R_xCo₄Sb₁₂ can be scaled by a function of the guest free distance r_GFD (the distance between R and Sb) and the atomic mass of R.

Fig. 4 The Inverse Pole Figure (IPF) maps obtained in EBSD measurements of In_0.8Co₄Sb₁₂.