Enhanced Thermoelectric Performance of GeTe-Based Composites Incorporated with Fe Nanoparticles

Incorporated nanoscale phases in thermoelectric (TE) materials can optimize the electronic and thermal transport properties to obtain high-performance TE materials. The rapid spark plasma sintering (SPS) technique is adopted to synthesize Ge_0.96Bi_0.06Te composites incorporated with soft magnetic Fe nanoparticles (nano-Fe) and their thermoelectric performance is researched in this study. With the phase transition of the Ge_0.96Bi_0.06Te matrix from the low-temperature rhombohedral phase to the high-temperature cubic one, the interface contact between Ge_0.96Bi_0.06Te and nano-Fe is transformed from Schottky contact to Ohmic one, which improves its electronic transport performance at high temperatures. At the same time, the additional Fe nanoprecipitation phonon scattering can reduce the lattice thermal conductivity to ∼0.66 W m^-1 K^-1. These mechanisms result in a high ZT value of 1.65 and a relatively highquality factor B of 1.05 at 785 K for Ge_0.96Bi_0.06Te/2 mol % Fe. This work suggests that the thermoelectric performance of composite materials can be enhanced by introducing a variable interface band structure.