Rapid preparations and thermoelectric properties of bulk skutterudites with in situ nanostructures

In this paper, Ge and Te co-doped skutterudites Co4Sb11Ge1-xTex were synthesized via two rapid preparation methods, melt quenching-spark plasma sintering (MQ-SPS) and high pressure-spark plasma sintering (HP-SPS). Bulk skutterudites can be synthesized in as little as 6 hours by MQ-SPS and under 1 hour by HP-SPS, as shown by both scanning electron microscopy and x-ray diffraction. This is a dramatic improvement over traditional methods requiring a full week of processing. The Seebeck coefficient, electrical conductivity and thermal conductivity across a temperature range of 300 to 800 K where measured. This work shows that the processing by HP-SPS significantly decreases thermal and lattice thermal conductivities, while increasing the temperature-dependent Seebeck maximum. Consequently, the HP-Co4Sb11Ge1-xTex samples show a higher dimensionless figure of merit compared with that of MQ-Co4Sb11Ge1-xTex samples throughout the measured temperature range.