Influence of ZnO Inclusions on the Low-Temperature Thermoelectric Properties of CoSb3

CoSb3 composites with different amounts of ZnO nanoparticles (2 wt.% to 12 wt.%) were prepared from nanosized ZnO (commercial) and micron-sized CoSb3 (obtained via solid-state reaction) particles mixed in solution and freeze dried. The resulting powders were densified by spark plasma sintering. The samples were characterized by x-ray diffraction and scanning electron microscopy. It was found that ZnO forms micron-sized clusters at the grain boundaries of the matrix material. The thermoelectric properties (electrical resistivity, thermopower, and thermal conductivity) were measured in the 2 K to 300 K temperature range. Both the electrical and thermal conductivities were observed to decrease with increasing ZnO content. The dimensionless figure of merit ZT was improved by up to 30% at 300 K for the sample containing 2 wt.% ZnO.