Enhanced Thermoelectric Performance of GeTe Materials via Compositing Fe ₃ O ₄ Nanoparticles

Recently, the ecofriendly thermoelectric (TE) material GeTe has garnered significant attention due to its excellent TE properties and potential applications. Despite the material's remarkable electrical transport properties, its intrinsically high carrier concentration limits the comprehensive improvement of TE properties. In this study, Fe₃O₄ nanoparticles were incorporated into a Ge_0.94Sb_0.06Te matrix to optimize its carrier concentration, resulting in a significant improvement in electrical conductivity (σ) and power factor (PF). The Ge_0.94Sb_0.06Te + 0.5 wt % Fe₃O₄ composite exhibited the maximum σ and PF values of 3020 S cm^-1 and 5000 μW m^-1 K^-2, respectively. The Fe₃O₄ precipitates accumulated at the grain boundaries, leading to a significant reduction in the thermal conductivity. Particularly, the lattice thermal conductivity reached a minimum value of 0.35 W m^-1 K^-1 at 773 K in the Ge_0.94Sb_0.06Te + 0.5 wt % Fe₃O₄ sample. Consequently, the highest figure of merit (<i>ZT</i>) of ≈2.0 was achieved at 773 K. Additionally, the average <i>ZT</i> over the operating temperature range of 323-773 K was approximately 1.2, and the single-leg efficiency reached about 8.4%, representing improvements of 110 and 200%, respectively, compared to the pure sample. This strategy effectively enables structural design at grain boundaries and can also be extended to other material systems.