Thermoelectric property of fine-grained CoSb3 skutterudite compound fabricated by mechanical alloying and spark plasma sintering

Skutterudite CoSb3 polycrystalline materials were prepared using a combined process of mechanical alloying ( MA) and spark plasma sintering ( SPS). The influence of SPS temperature on the thermoelectric properties was focused in this work with a special emphasis on the analysis of the size effects of grains. The average grain sizes decreased from 300 to 50 nm with decreasing SPS temperatures from 600 to 300 degrees C. The electrical resistivities of samples spark plasma sintered at 300-600 degrees C all decreased with increasing temperature, indicating a classic intrinsic conduction behaviour of semiconductors. The samples spark plasma sintered at 300-500 degrees C showed a positive Seebeck coefficient while the sample spark plasma sintered at 600 degrees C showed a negative Seebeck coefficient. The room-temperature thermal conductivities were reduced from 4.30 to 2.92 W m(-1) K-1 as the grain sizes were decreased from 300 to 100 nm corresponding to SPS at 600 and 400 degrees C, respectively. The present work indicates that MA and SPS is a good combination for fabricating fine-grained CoSb3 thermoelectric materials.