Nanophase oxalate precursors of thermoelectric CoSb3 by controlled coprecipitation predicted by thermodynamic modeling.

The precursors for the formation of thermoelectric skutterudite CoSb 3 nanoparticles are predicted by thermodynamic modeling of the complex chemical species. Based on the results, equimolar mixture of CoC 2 O 4 ·2H 2 O and Sb(C 2 O 4 )OH are successively co-precipitated under controlled conditions of pH = 2.7 and concentration of reactants. The as synthesized powder was decomposed at 350 °C to remove the organic molecules and further reduced to CoSb 3 phase by heating at 530 °C under hydrogen flow. The obtained powder was consolidated by spark plasma sintering (SPS). CoSb 3 prepared by controlled chemical co-precipitation has p-type behavior with a positive sign of the Seebeck coefficient. TE transport properties were measured, which revealed that the Seebeck coefficient increased 2.5 times with increasing the temperature and it is lower than the ball milled CoSb 3 . Thermal conductivity of sintered CoSb 3 at 773 K starts from 0.06 W/cm K at room temperature and decreases to 0.04 W/cm K at 700 K, which is lower than the bulk counterpart. The ZT of coprecipitated CoSb 3 and SPS consolidated at 773 K shows 2 times higher than the ball milled one. [ABSTRACT FROM AUTHOR]