High-Pressure Synthesis and Thermoelectric Properties of Partially Filled Skutterudites RxCo4Sb12 (R = In, Tb and Dy)

Partially filled skutterudite compounds RxCo4Sb12 (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 In0.8Co4Sb12 is 2-5 mu m. 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 In0.8Co4Sb12 at 300 K. We studied guest ion R dependence of lattice thermal conductivity kappa L for RxCo4Sb12 systematically based on a simple model for the rattling. The reduction rate of kappa L of RxCo4Sb12 can be scaled by a function of the guest free distance rGFD (the distance between R and Sb) and the atomic mass of R.

Automated summary

Partially filled skutterudite compounds RxCo4Sb12 (R = In, Tb and Dy, nominal composition 0.1 <= x <= 1.5) were synthesized under high pressure. The samples were characterized by XRD and SEM-EDX, and the highest filling fractions for In, Tb, and Dy were determined. Electrical and thermal properties were measured, and the ZT value of 0.10 was obtained for In0.8Co4Sb12 at 300 K. Additionally, the dependence of lattice thermal conductivity on the guest ion R was systematically studied.