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The recent growing energy crisis draws considerable attention to high‐performance thermoelectric materials. n‐type bismuth telluride is still irreplaceable at near room temperature for commercial application, and therefore, is worthy of further investigation. In this work, nanostructured Bi2Te3 polycrystalline materials with highly enhanced thermoelectric properties are obtained by alkali metal Na solid solution. Na is chosen as the cation site dopant for n‐type polycrystalline Bi2Te3. Na enters the Bi site, introducing holes in the Bi2Te3 matrix and rendering the electrical conductivity tunable from 300 to 1800 Scm–1. The solid solution limit of Na in Bi2Te3 exceeds 0.3 wt%. Owing to the effective solid solution, the Fermi level of Bi2Te3 is properly regulated, leading to an improved Seebeck coefficient. In addition, the scattering of both charge carriers and phonons is modulated, which ensured a high‐power factor and low lattice thermal conductivity. Benefitting from the synergistic optimization of both electrical and thermal transport properties, a maximum figure of merit (ZT) of 1.03 is achieved at 303 K when the doping content is 0.25 wt%, which is 70% higher than that of the pristine sample. This work disclosed an effective strategy for enhancing the performance of n‐type bismuth telluride‐based alloy materials. [ABSTRACT FROM AUTHOR]

• PbBr 2 doped n -type polycrystalline SnSe that forms multi-nanoprecipitates. • The carrier concentration increased to 1.79 × 1019 cm−3 at room temperature. • The thermal conductivity decreased to 0.32 Wm−1K−1 at 773 K. • A ZT peak reaches 1.1 at 773 K along the parallel to SPS pressure direction. Both p - and n -type SnSe single crystals have been reported to possess high thermoelectric performances, thus highlighting the possibility for commercialization. Polycrystalline SnSe that has better mechanical properties however possesses inferior thermoelectric properties compared to single crystal SnSe. In this work, n -type polycrystalline SnSe 0.95 + x wt% PbBr 2 (x = 0, 0.5, 1, and 1.5) samples were synthesized by combining mechanical alloying and spark plasma sintering technology. The effects of PbBr 2 doping on thermoelectric performance of SnSe were studied in detail. The results show that the carrier concentration was dramatically increased from 2.51 × 1017 cm−3 in pure SnSe 0.95 to 1.79 × 1019 cm−3 in SnSe 0.95 + 1.5 wt% PbBr 2 , further resulting in an enhanced electrical conductivity. Multi-nanoprecipitates are present in the samples, including SnO, SnPb and SnBr x O y , which possibly affect the Seebeck coefficient and the lattice thermal conductivity. A peak ZT value of 1.1 was obtained at 773 K for the SnSe 0.95 + 1.0 wt% PbBr 2 sample. This work highlights that PbBr 2 is an effective dopant to improve the TE performance of n -type polycrystalline SnSe. [ABSTRACT FROM AUTHOR]

InGaO 3 (ZnO) m (m = 1, 2, 3, 4, and 5) ceramics are a series of n-type oxide thermoelectric materials with layered structures and low thermal conductivities. Herein, InGaO 3 (ZnO) m (m = 1, 2, 3, 4, and 5) ceramics were fabricated by spark plasma sintering (SPS). Two different trends in the thermoelectric properties of the InGaO 3 (ZnO) m (m = 1, 2, 3, 4, and 5) ceramics were observed depending on the odevity of the m value. The InGaO 3 (ZnO) sample exhibited a relatively high electrical conductivity and was therefore selected for vacuum annealing to further improve the electrical transport performance. Oxygen vacancy defects were introduced to the matrix during the annealing procedure, which improved the thermoelectric performance. A maximum ZT of 0.45 was obtained at 973 K for the InGaO 3 (ZnO) sample with a 96 h vacuum annealing treatment, which is 30 times higher than that of the pristine sample. [ABSTRACT FROM AUTHOR]

The recent growing energy crisis draws considerable attention to high‐performance thermoelectric materials. n‐type bismuth telluride is still irreplaceable at near room temperature for commercial application, and therefore, is worthy of further investigation. In this work, nanostructured Bi2Te3 polycrystalline materials with highly enhanced thermoelectric properties are obtained by alkali metal Na solid solution. Na is chosen as the cation site dopant for n‐type polycrystalline Bi2Te3. Na enters the Bi site, introducing holes in the Bi2Te3 matrix and rendering the electrical conductivity tunable from 300 to 1800 Scm–1. The solid solution limit of Na in Bi2Te3 exceeds 0.3 wt%. Owing to the effective solid solution, the Fermi level of Bi2Te3 is properly regulated, leading to an improved Seebeck coefficient. In addition, the scattering of both charge carriers and phonons is modulated, which ensured a high‐power factor and low lattice thermal conductivity. Benefitting from the synergistic optimization of both electrical and thermal transport properties, a maximum figure of merit (ZT) of 1.03 is achieved at 303 K when the doping content is 0.25 wt%, which is 70% higher than that of the pristine sample. This work disclosed an effective strategy for enhancing the performance of n‐type bismuth telluride‐based alloy materials. [ABSTRACT FROM AUTHOR]

The decrease in lattice thermal conductivity is one of the most effective methods for enhancing thermoelectric properties. Achieving lattice thermal conductivity close to the theoretical limit is extremely difficult while maintaining an impressive power factor. By introducing ultrafine bismuth sulfide nanograins, strong phonon scattering was generated by associated multiscale lattice defects to further gain a low lattice thermal conductivity of 0.244 W/m/K approaching Clarke's limitation of 0.242 W/m/K. Simultaneously, the electrical conductivity was increased by S diffusion and suppression of the antisite defects, and a high power factor was maintained to produce an improved ZT peak of 1.2 at 473 K for the Bi 2 Te 2.7 Se 0.3 + 1 wt % Bi 2 S 3 #2 sample. This sample was used to fabricate a small device with a p-leg, and the direct conversion efficiency reached 4.39%. Inverse changes in hardness and Young's modulus in conjunction with Bi 2 S 3 content are first reported in thermoelectric materials, which has potential assistance in synchronously improving their mechanical and thermoelectric properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Polycrystalline SnSe thermoelectric materials have received extensive interests owing to the low thermal conductivity and available mechanical properties. However, the low electrical conductivity seriously hinders its application. In this work, stemming from the introducing of Hf and Cl substitution, they released more electrons. Owing to the improved carrier concentration, a high electrical conductivity of 33 S cm−1 for the SnSe 0.95 +1 wt%HfCl 4 sample was obtained at 773 K, about 5 times as much as that of the SnSe 0.95 sample. Thus, a peak power factor of 553.8 μW m−1 K−2 of SnSe 0.95 +3 wt%HfCl 4 sample at 773 K was obtained. Meanwhile, the phonon scattering was enhanced due to the decrease of grain size, the lattice thermal conductivity was suppressed. The pretty low κ l of 0.33 W m−1 K−1 was obtained at 773 K for the SnSe 0.95 +4 wt%HfCl 4 sample. Consequently, the peak ZT value of ∼1.1 was achieved for SnSe 0.95 +3 wt%HfCl 4 sample at 773 K. • (Hf, Cl) co-doping in polycrystalline SnSe bulk samples were fabricated via melting method and combined with the spark plasma sintering (SPS) method. • Due to the introduced Hf and Cl substitution, the more electronic was released, a high electrical conductivity of 33 S cm−1 for the SnSe 0.95 +1 wt%HfCl 4 sample was obtained at 773 K. • Owing to the decreased grain size and the enhanced phonon scattering, a low κ l of 0.33 Wm−1 K−1 was obtained at 773 K for the SnSe 0.95 +4 wt%HfCl 4 sample. [ABSTRACT FROM AUTHOR]

Both single crystal and polycrystalline SnSe have been widely investigated due to their superior thermoelectric properties in the medium temperature range. Due to its poor mechanical properties and complex and time-consuming synthesis process, single crystal SnSe is difficult to apply commercially. In this work, n-type polycrystalline SnSe with high thermoelectric properties was fabricated by LaCl 3 doping via the melting method combined with the spark plasma sintering (SPS) technique. Surprisingly, it was found that the different doping processes affect the electrical behavior of LaCl 3 -doped polycrystalline SnSe. The sample of LaCl 3 -doped SnSe was p-type when ball milling and the SPS technique were employed in our previous work, and the sample was n-type when the melting method and SPS were employed in this work. The doping mechanism was investigated in detail in this work. [Display omitted] • LaCl 3 -doped SnSe was fabricated via the melting method and SPS. • The dopant atom position in SnSe lattice depends on the synthesis process. • Power factor of 562 ​μWm−1K−2 ​at 773 ​K was achieved in n-type polycrystalline SnSe. • The highest ZT of 0.85 ​at 773 ​K was achieved in SnSe 0.95 +1 ​wt% LaCl 3 at 773 ​K. [ABSTRACT FROM AUTHOR]