Thermoelectric properties of partially filled skutterudites R_x Co₄Sb₁₂ (R = Ce and Nd) synthesized under high pressures

Abstract

We report the thermoelectric properties of the partially Ce or Nd filled skutterudite compounds Ce x Co 4 Sb 12 and Nd x Co 4 Sb 12 prepared under high pressures and temperatures. The samples were characterized by X-ray diffraction. The actual filling ratio x of Ce or Nd was estimated by scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDX). SEM-EDX results indicate that the maximum x values of Ce and Nd can be increased to 0.37 and 0.33, respectively. These values have been considered the highest for any Ce x Co 4 Sb 12 and Nd x Co 4 Sb 12 reported thus far. The electrical resistivity, thermal conductivity, and Seebeck coefficient measurements of the compounds were performed from 5 to 760 K. Furthermore, the Hall coefficient and specific heat of the compounds were also measured below 300 K. The Seebeck and Hall coefficients of both Ce-and Nd-filled samples exhibited the n-type conductor behavior. The maximum dimensionless figure-of-merit (ZT) values of Ce x Co 4 Sb 12 and Nd x Co 4 Sb 12 were determined to be 0.26 and 0.48 at 700 K, respectively.

High-Pressure Synthesis and Thermoelectric Properties of Partially Filled Skutterudites <i>R_x</i>Co₄Sb₁₂ (<i>R</i> = In, Tb and Dy)

“…This behavior often occurs in similar experiments using a high-pressure synthesis. 11,13) As shown in Fig. 3(a), the lattice constant for Tb x Co 4 Sb 12 increases with the increase of the nominal Tb doping ratio x.…”

“…The details about the preparation are described in our previous papers. 11,13,28) The reaction temperature and pressure were 600610°C and 24 GPa.…”

Effect of partial Yb filling on thermoelectric properties of skutterudite compound RhSb3

“…We prepared a large bulk sample using SPS technique and the powdered samples of Yb 0.7 Rh 4 Sb 12 synthesized under high pressure as a starting materials for the evaluation of the TE properties at high temperature region above 300 K. In the previous work, the use of the SPS technique using powder samples prepared under high pressure caused a reduction in the filling ratio of guest ions. 27) Therefore, we chose Yb 0.7 Rh 4 Sb 12 with a higher actual filling ratio (0.43) than Yb 0.8 Rh 4 Sb 12 (0.39) which shows the highest ZT value at 300 K. Furthermore, Yb 0.7 Rh 4 Sb 12 includes no secondary phases (RhSb 2 and Sb). After SPS, the actual filling ratio of Yb decreased to 0.27.…”

Synthesis Optimization and Thermoelectric Properties of S-Filled and Te-Se Double-Substituted Skutterudite under High Pressure

“…4 Therefore, the chemical formula of filled skutterudite can be written as phonons of the heat-carrying lattice and inhibiting its thermal conductivity. Common filling atoms R include the alkali metal (Li), 5 alkaline earth metals (Mg, Ba, Ca), 6−8 rare earth elements (Ce, Nd, Yb), 9,10 and other filling elements (Sn, Ge). 11−13 The Jet Propulsion Laboratory in the United States has conducted extensive research on skutterudite compounds and developed ternary skutterudite compounds.…”

“…Due to the weak chemical bond between the filled atom and the surrounding Sb atom, the material exhibits unique vibration behavior in the gap, strongly scattering the phonons of the heat-carrying lattice and inhibiting its thermal conductivity. Common filling atoms R include the alkali metal (Li), alkaline earth metals (Mg, Ba, Ca), − rare earth elements (Ce, Nd, Yb), , and other filling elements (Sn, Ge). − …”