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

Abstract

Partially filled skutterudite compounds YbxRh4Sb12 (0 ≤ x ≤ 0.8 as nominal values) were synthesized under high pressure using a cubic anvil press. The samples were characterized by X-ray diffraction and scanning electron microscope with energy-dispersive X-ray microanalyser. Actual Yb filling ratio x of YbxRh4Sb12 increases up to 0.44, which is higher than the values for any samples prepared at ambient pressure. Thermoelectric properties of YbxRh4Sb12 were investigated in the temperature range of 2–700 K. The electrical resistivity of YbxRh4Sb12 exhibits semiconducting behavior. The resistivity decreases with increasing x. By Yb filling, the lattice thermal conductivity markedly decreases to 2.5 Wm−1 K−1 at room temperature, from 8.2 Wm−1 K−1 of unfilled RhSb3. The Seebeck coefficient shows a negative value (n-type conductivity). The highest dimensionless figure of merit ZT of YbxRh4Sb12 was determined to be 0.1 at 420 K for the compound with x = 0.27. The power factor is large (more than 10−3 Wm−1 K−2) over a wide temperature range between 250 and 450 K.