Effect of spark plasma sintering and Sb doping on the thermoelectric properties of Co4Ge6Te6 skutterudite

Highlights: • High-quality samples of the ternary skutterudite Co₄Ge₆Te₆ has been prepared using spark plasma sintering. • Use of insulating Mica films prevents sample decomposition from the direct current during spark plasma sintering. • Structure and thermoelectric properties of the pristine and Sb-doped Co₄Ge₆Te₆ samples have been established. • Sb-doped samples show significant increase in the power factor. -- Abstract: For high-performance thermoelectric material, spark plasma sintering (SPS) has been widely used to manufacture specimens in a very short period compared to other sintering techniques. However, the microstructural evolution, phase stability and compositional homogeneity of thermoelectric materials under SPS conditions have been rarely investigated. In this work, we studied the effect of SPS on microstructure, phase homogeneity and thermoelectric properties of the ternary Co₄Ge₆Te₆ skutterudite. Phase homogeneity of the spark plasma sintered Co₄Ge₆Te₆ pellets was investigated by X-ray microdiffraction and SEM/EDS analyses. Significant variations in the physical properties reflect presence of different crystalline phases due to the current-driven decomposition inside the samples. Use of the electrically insulating Mica film prevents the current from passing through the sample and yields high-quality samples. Furthermore, small amounts of Sb, added to investigate the role of dopants on the physical properties, yielded the highest power factors for the Co₄Ge₆Te₆-based compounds.