Large figure of merit <i>ZT</i> = 1.88 at 873 K achieved with nanostructured Si_0.55Ge_0.35(P_0.10Fe_0.01)

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.