Enhancement in thermoelectric performance of bulk CrSi2 dispersed with nanostructured SiGe nanoinclusions

Abstract

CrSi2 is recognized as potential thermoelectric material for mid-temperature energy generation applications owing to its high temperature chemical stability coupled with its cost-effective and non-toxic constituent elements. However, its thermoelectric performance has been reported to be limited owing to its high thermal conductivity, which is reported to dominate by its lattice counterpart. In the present studies, we realize a state-of-the-art (ZT)max ∼ 0.32 at 673 K in an optimized nanocomposite composition of CrSi2/7.5 wt%SiGe, synthesized using spark plasma sintering of bulk CrSi2 dispersed with SiGe nanoparticles (crystallite size ∼12 nm). The incorporation SiGe nanoparticles in bulk CrSi2 resulted in a significant reduction in its thermal conductivity owing to enhanced scattering of heat-carrying phonons by a high density of nanoscale interfaces. Concurrently, the power factor of the nanocomposite was also found to increase due to an increase its carrier concentration and mobility on dispersion of SiGe nanoparticles in the CrSi2 matrix. Thus, the favorable tuning of the electrical and thermal transport properties led to a ZT∼ 0.32 which is ∼125% higher than its pristine counterpart. The as-synthesized pristine and nanocomposites were characterized employing X-ray diffraction and field emission scanning electron microscopy, based on which the enhancement in their thermoelectric properties has been discussed.