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

Abstract

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 (FeSi₂). The dimensionless thermoelectric figure of merit (ZT) of the nanocomposite material was higher than the peak ZT of the conventional single phase Si_0.80Ge_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_0.88Ge_0.12)_0.925–(FeSi₂)_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-FeSi₂ nanoparticles in the microstructure.