Chemical alloying and characterization of nanocrystalline Co1-xNixSb3-yTey skutterudites

Novel chemical alloying approach has been developed for the fabrication of nanocrystalline Co_1-xNi_xSb_3-yTe_y skutterudites. The approach has compromised solution chemical synthesis and thermochemical processing under controlled conditions. All of the required elements, Co, Ni, Sb and Te were coprecipitated from an aqueous solution of their salts to produce a precursor with a well-defined composition, fine particle size, high homogeneity, low crystallinity and high reactivity. After calcination and hydrogen reduction of the precursor at moderate temperature of 450°C for 2 hrs, these elements were alloyed into Co_1-xNi_xSb_3-yTe_y skutterudite of high purity and nano-grain size. These nanocrystalline materials have demonstrated very low thermal conductivities and enhanced thermoelectric performance. Thermal conductivity values of skutterudite have been reduced by 25-75% over polycrystalline materials. With a combined doping by Ni and Te, a ZT value of 0.65 at 700 K has been obtained for the sample of Co_0.92Ni_0.08Sb_2.988Te_0.012.