Abstract
P-type skutterudites, with nominal compositions YbxFe3.5Ni0.5Sb12 (0.8 ≤ x ≤ 1), have been
synthesized by induction melting with subsequent annealing, and their thermoelectric properties
evaluated from 3.5 K to 745 K to assess their suitability for thermoelectric based waste heat recovery
applications. We report results for the synthesis and measurements of Seebeck coefficient (S),
electrical resistivity (ρ), thermal conductivity (κ), Hall coefficient (RH), and effective mass (m*/m0) of
YbxFe3.5Ni0.5Sb12 (0.8 ≤ x ≤ 1). Powder x-ray diffraction and electron probe microanalysis (EPMA)
show that this system has a narrow filling fraction range of x ~ 0.84 to 0.86 for Yb in the
crystallographic voids. All samples show positive RH for the entire temperature range studied with
carrier concentrations ranging from 9.6×1020 to 2.8×1021 cm-3 at room temperature. Relatively high
values of S result in high power factors up to 17 μWcm-1K-2 at room temperature. However, large
values of κ and a sharp reduction in the S at high temperature due to bipolar conduction prevent the
attainment of high thermoelectric figure of merit.
