Enhanced thermoelectric performance in a metal/semiconductor nanocomposite of iron silicide/silicon germanium

Hypothetical efficient thermoelectrics based on nanoparticles in alloys of silicide nanocomposites were predicted by Mingo et al. This investigation presents the experimental realization of an n-type silicon germanium alloy with an embedded metallic α-phase iron silicide (FeSi 2 ). The dimensionless thermoelectric figure of merit ( ZT ) of the nanocomposite material was higher than the peak ZT of the conventional single phase Si 0.80 Ge 0.20 over a broad temperature range (650-1000 °C) while consuming smaller amounts of germanium. The addition of 2.5% silver to the nanocomposite, which acted as a sintering aid, reduced the sintering temperature and resulted in smaller thermal conductivity. The optimum material composition of (Si 0.88 Ge 0.12 ) 0.925 -(FeSi 2 ) 0.05 -Ag 0.025 was found after investigation of a large number of nanocomposite materials. The combination of X-ray diffraction, energy-dispersive X-ray spectroscopy, and transmission electron microscopy analysis confirmed a uniform distribution of α-FeSi 2 nanoparticles in the microstructure. The metal-semiconductor nanocomposite of n-type thermoelectric SiGe-FeSi 2 was successfully developed and characterized versus electrical, thermal, and microstructural properties.