Effect of Nanostructuring on the Thermoelectric Properties of Co0.97Pd0.03Sb3

We synthesized n-type CeO2/Co0.97Pd0.03Sb3 composites with nanometric grain sizes (200 nm to 300 nm) by spark plasma sintering in order to promote phonon scattering at grain boundaries. Powdered samples were initially obtained by ball milling Co0.97Pd0.03Sb3 together with x vol.% (x = 0, 0.5, 1, 2) of CeO2 nanoparticles. This additive slows down the grain size growth of the skutterudite matrix which occurs during sintering, thereby contributing to phonon scattering. The nanostructured samples display reduced Hall electron concentration compared with that of the reference Co0.97Pd0.03Sb3 because of Fe contamination by the steel balls and vials. However, the electronic transport properties are nearly identical to those of Co0.98Pd0.02Sb3, which allows for comparison with this latter compound. The lattice thermal conductivity is strongly decreased in nano-Co0.97Pd0.03Sb12 (−40% at 300 K). This results in an enhanced (+32%) ZT value peaking at 0.65 at 650 K in nano-Co0.97Pd0.03Sb12 + 2% CeO2 when compared with micro-Co0.98Pd0.02Sb3.