Large figure of merit ZT = 1.88 at 873 K achieved with nanostructured Si0.55Ge0.35(P0.10Fe0.01)

Abstract

High-performance Si-Ge-based thermoelectric materials were prepared simultaneously using nano-structuring and electronic structure modifications. Density functional theory calculations predicted that Fe atoms in the Si-Ge alloy would constructively modify the electronic structure to significantly increase the Seebeck coefficient, experimentally confirmed as |S| > 517 ± 20 μV K-1 at 673 K. Dense bulk samples made of nano-grains possessed very small thermal conductivity, κ < 0.80 ± 0.10 W m-1 K-1 at T < 873 K. Very large ZT values exceeding 1.00 were obtained in the temperature range 710 K < T < 873 K, with a maximal value of 1.88 at 873 K.