We theoretically find that embedding silicide nanoparticles in SixGe1-x alloys is able to considerably improve the figure of merit (ZT). We have computed the thermal conductivity as a function of the sizes of NiSi2 and CoSi2 nanoparticles. We find that the optimal nanoparticle diameters minimizing the composite’s thermal conductivity are 6.9 nm for NiSi2 and 12.6 nm for CoSi2 at room temperature. We provide validity ranges of nanoparticle volume fractions that will not reduce the thermoelectric power factor, but will considerably decrease the thermal conductivity. Embedding NiSi2 or CoSi2 nanoparticles in SixGe1-x may lead to a 5-fold increase of figure of merit (ZT ∼ 0.5) at room temperature and 2.8 times increase (ZT ∼ 2.0) at 900 K. The proposed materials with high figures of merit are promising candidates to be used in integrated micro refrigerators in chips and thermoelectric power generation and waste heat recovery.

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