A high-performance thermoelectric oxyselenide BiCuSeO ceramic with ZT > 1.1 at 823 K and higher average ZT value (ZTave ≈0.8) is obtained. The heavy doping element and nanostructures can effectively tune its electronic structure, hole concentration, and thermal conductivity, resulting in substantially enhanced mobility, power factor, and thus ZT value. This work provides a path to high-performance thermoelectric ceramics.

The low power factor (PF) of BiCuSeO oxyselenide inhibits further improvement on thermoelectric figure of merit in the moderate temperature range. In this Letter, we show that the electron transport properties of doped BiCuSeO oxyselenide can be accurately described in acoustic phonon scattering assumption within the framework of single parabolic band model. It is further found that the doping elements alter the electron transport properties by tuning the effective mass and deformation potential. Based on these understandings, we argue that the higher power factor can be achieved by choosing the doping element based on reducing deformation potential coefficient and decreasing effective mass.

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Bi1−xLaxCuSeO ceramic bulks have been prepared by the spark plasma sintering method. Our results indicate that La-doping can lead to an obvious change of the band structure evidenced by the absorption spectra and electric transportation behaviors (e.g., m* and Seebeck coefficient). The variation of band structure results in a great enhancement of carrier mobility caused by a decreased energy offset between the primary and secondary valence bands. A maximum ZT value of 0.74 can be obtained in 8% La-doped BiCuSeO sample at 923 K, which is 37% higher than that of the pure BiCuSeO bulk. Our results reveal that band engineering is an effective way to enhance the thermoelectric properties of BiCuSeO system.

Polycrystalline Bi2−xO2Se ceramics were synthesized by spark plasma sintering process. Their thermoelectric properties were evaluated from 300 to 773 K. All the samples are layered structure with a tetragonal phase. The introduction of Bi deficiencies will cause the orientation alignment and change of effective mass. As a result, a significant enhancement of thermoelectric performance was achieved. The maximum of Seebeck coefficient is −568.8 μV/K for Bi1.9O2Se at 773 K, much larger than −445.6 μV/K for pristine Bi2O2Se. Featured with very low thermal conductivity [~0.6 W·(m·K)−1] and an optimized electrical conductivity, ZT at 773 K is significantly increased from 0.05 for pristine Bi2O2Se to 0.12 for Bi1.9O2Se by introducing Bi deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.

A high‐performance thermoelectric BiCuSeO oxyselenides has been prepared by a simple fabrication approach. Phase composition and microstructure analysis indicate that the obtained ceramic samples are almost BiCuSeO phase with plate structure. Our results show that Pb‐doped BiCuSeO bulks have good electrical conductivity, large Seebeck coefficient, and low thermal conductivity. A large power factor ~672 μ/Wm/K2 at 573 K can be observed in the BiCuSeO ceramic by the 10% Pb doping, and the dimensionless figure of merit (ZT) can reach 0.95 at 873 K, which makes them promising candidates for thermoelectric applications.