Realizing High Thermoelectric Performance in n-Type Se-Free Bi₂Te₃ Materials by Spontaneous Incorporation of FeTe₂ Nanoinclusions

Bi₂Te₃-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature. However, the stability of existing n-type Bi₂(Te,Se)₃ materials is still low due to the evaporation energy of Se (37.70 kJ mol⁻¹) being much lower than that of Te (52.55 kJ mol⁻¹). The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency. Here, we have developed a new approach for the high-performance and stable n-type Se-free Bi₂Te₃-based materials by maximizing the electronic transport while suppressing the phonon transport, at the same time. Spontaneously generated FeTe₂ nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity. The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles. With a fine-tuning of the fermi level with Cu doping in the n-type Bi₂Te₃–0.02FeTe₂, a high power factor of ~41 × 10⁻⁴ Wm⁻¹ K⁻² with an average zT of 1.01 at the temperature range 300–470 K are achieved, which are comparable to those obtained in n-type Bi2(Te,Se)₃ materials. The proposed approach enables the fabrication of high-performance n-type Bi₂Te₃-based materials without having to include volatile Se element, which guarantees the stability of the material. Consequently, widespread application of thermoelectric devices utilizing the n-type Bi₂Te₃-based materials will become possible.