With texturing by re-pressing, the peak ZT was increased to 1.06. Aging in air for over 5 months did not deteriorate but further improved the peak ZT to 1.10. The mechanism by which copper improves the reproducibility, enhances the carrier mobility, and reduces the lattice thermal conductivity is also discussed.

By adding aluminium (Al) into lead selenide (PbSe), we successfully prepared n-type PbSe thermoelectric materials with a figure-of-merit (ZT) of 1.3 at 850 K. Such high ZT is achieved by a combination of high Seebeck coefficient caused by very possibly the resonant states in the conduction band created by Al dopant and low thermal conductivity from nanosized phonon scattering centers. Broader contextThermoelectric devices directly convert heat to electricity, thus they are important for harvesting natural heat as well as waste heat. For efficient devices, high figure-of-merit (ZT) materials are desired. We report here n-type lead selenide (PbSe) thermoelectric materials with ZT of 1.3 at 850 K. These materials are prepared by adding aluminium (Al) in PbSe during ball milling and hot pressing. Al, as a dopant in PbSe, possibly creates resonant states in the conduction band and causes increase in the local density of states (DOS) near the Fermi level. As a result, the Seebeck coefficients of Al added PbSe samples are about 40~100% higher than the predicted values by the simple parabolic band model and about 40% higher than the Cl-doped reference PbSe sample without resonant states. Furthermore, using ball milling and hot pressing technique, the structure of our samples contains features such as Pb depleted discs, small grains, and ~10 nm subgrains that are effective for phonon scattering, and result in a much lower lattice thermal conductivity of 0.6~0.7 Wm

Achieving higher carrier mobility plays a pivotal role for obtaining potentially high thermoelectric performance. In principle, the carrier mobility is governed by the band structure as well as by the carrier scattering mechanism. Here, we demonstrate that by manipulating the carrier scattering mechanism in n-type MgSb-based materials, a substantial improvement in carrier mobility, and hence the power factor, can be achieved. In this work, Fe, Co, Hf, and Ta are doped on the Mg site of MgSbBiTe, where the ionized impurity scattering crosses over to mixed ionized impurity and acoustic phonon scattering. A significant improvement in Hall mobility from ∼16 to ∼81 cm⋅V⋅s is obtained, thus leading to a notably enhanced power factor of ∼13 μW⋅cm⋅K from ∼5 μW⋅cm⋅K A simultaneous reduction in thermal conductivity is also achieved. Collectively, a figure of merit () of ∼1.7 is obtained at 773 K in MgCoSbBiTe The concept of manipulating the carrier scattering mechanism to improve the mobility should also be applicable to other material systems.

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