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[Display omitted] • Superstructured Zr-rich nanoprecipitates are generated from ZrNiSn-based alloys. • Coherent interface can scatter phonons and filter low-energy carriers. • Numerous dislocations can be produced by the superstructures. • The thermal and electrical properties are successfully decoupled. By adjusting the composition of half-Heusler (HH) alloys to deviate from the stoichiometric ratio, the generation of numerous full-Heusler (FH) nano-sized precipitates in the matrix is an effective method to improve its thermoelectric performance. However, it is difficult to control the size and shape of FH nanoprecipitates in the HH matrix and thus, to limit the substantial improvement in the thermoelectric properties. In this study, we discovered that some regular hexagonal nanoparticles with grain sizes of 10–50 nm were generated from the ZrNiSn matrix when Zr was in excess. The generation of coherent interfaces between the ZrNiSn matrix and Zr-rich nanoprecipitates can effectively scatter medium-frequency phonons and filter low-energy carriers, leading to a drastically reduced lattice thermal conductivity, improved carrier mobility, and retained Seebeck coefficient. Significantly, the extra Zr-rich nanoprecipitates with superstructures can generate dislocations to scatter medium-frequency phonons to further reduce the lattice thermal conductivity. Furthermore, the Zr-rich precipitates can inject a large number of carriers into the matrix, thereby improving the electrical conductivity. As a result, the interdependence between the electrical and thermal parameters was successfully decoupled by the generation of Zr-rich precipitates, thus leading to a notable enhancement of the thermoelectric performance of ZrNiSn-based alloys. [ABSTRACT FROM AUTHOR]

• Nanoporous SnSe with QDs was fabricated by magnetic field-assisted solution synthesis. • Electrical and thermal transport properties are synergistically optimized by introducing QDs and nanopores. • High peak ZT of 2.0 and average ZT of 0.74 are achieved in Polycrystalline SnSe. SnSe is considered as one of the most promising candidates for thermoelectric application because of its attractive performance recently. In this work, a high magnetic field (5 T) is applied during the solution synthesis process. With the assist of the high magnetic field, nanopores and quantum dots (Sn, Se) are induced in the Ga doped p-type polycrystalline SnSe. It is found that an ultralow lattice thermal conductivity of 0.19 W m−1 K−1 is caused by enhanced phonon scattering due to the presence of nanopores, quantum dots, lattice strain in dislocation networks. The enhanced density of states induced by Sn and Se quantum dots contributes to enhanced Seebeck coefficient. The enhanced electrical conductivity and Seebeck coefficient give rise to a significant enhancement in power factor over the whole temperature range. The maximum power factor reaches to 6.12 μW cm−1 K−2 at 873 K for the sample prepared under high magnetic field. Consequently, a peak ZT of 2.0 as well as a high average ZT of 0.74 (300–873 K) is achieved in 5 T -NP/QD Sn 0.975 Ga 0.025 Se sample. This study provides an important direction for developing high performance thermoelectric materials by structural manipulation with the aid of high magnetic field in solution chemistry. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile one-pot hydrothermal method for making micro/nano Cu 2-x S has been presented. • Significant reduced thermal conductance in micro/nano pellets has been observed. • A ZT of 1.1 at 773 K was found, higher than the reported Cu 2-x S by chemical method. • The work can re-stimulate the use of microstructure engineering for TE applications. Among the state-of-the-art thermoelectric materials, copper sulfides (Cu 2 S) have been predicted as promising thermoelectric materials due to their low intrinsic thermal conductivity. However, they still confront the problems with lower electrical properties, which distinctly restrict their thermoelectric application. Significant enhancement of thermoelectric properties is a great challenge owing to the common interdependence of electrical and thermal conductivity. Herein, a micro/nano Cu 2-x S composite, with significantly enhanced thermoelectric properties, is prepared via a simple hydrothermal method. Due to the synergistic effect of the introduced nanostructure and the increased Cu 1.96 S contents, the micro/nano Cu 2-x S bulk samples present a power factor of 10.1 μW cm−1 K−2 at 773 K. Meanwhile, a decrease of the thermal conductivity to 0.69 W m−1 K−1 is obtained, originating from the strong phonon scattering of micro/nano structure. Remarkably, a ZT max value of 1.1 at 773 K is obtained, which is higher than the reported Cu 2-x S thermoelectric material using chemical methods. This study proposes a facile microstructure engineering strategy for the development of high-performance thermoelectric materials. [ABSTRACT FROM AUTHOR]

A unique method taking advantage of a synergistic effect at (LaVO 3)/Cu 0.07 Bi 0.5 Sb 1.5 Te 3 interfaces to boost the thermoelectric figure of merit is demonstrated. The unusual electrical conductivity and energy filtering effect largely help to improve power factor and reduce thermal conductivity of the composites. As a result, a high ZT of 1.26 and ZT avg of 1.13 are successfully achieved. [Display omitted] • Mott insulator LaVO 3 (LVO) was added into Cu 0.07 Bi 0.5 Sb 1.5 Te 3 (BST) to boost the ZT. • LVO/BST interface produces an unusual high σ and enhanced energy filtering effect. • Addition of LVO helps to reduce both the bipolar and lattice thermal conductivity. • A high ZT of 1.26 and ZT avg of 1.13 are successfully achieved. • Mechanical properties of the composites are greatly enhanced by the addition of LVO. The enhancement of thermoelectric (TE) figure of merit, ZT, is of great essence to improve the efficiency of TE devices since the commercial applications of TE devices have been constrained due to low performance. Here, we report a novel approach for ZT improvement via a synergistic effect of unusual conducting behavior and energy filtering at the (LaVO 3)/Cu 0.07 Bi 0.5 Sb 1.5 Te 3 incoherent interfaces. In this work, the incoherent interfaces have been engendered by the incorporation of LaVO 3 (LVO) nanoparticles into Cu 0.07 Bi 0.5 Sb 1.5 Te 3 (BST) matrix, inducing a remarkable enhancement in electrical conductivity due to defect formations and an insulator-to-metal transition. This induced conducting behavior also eminently suppressed the adverse intrinsic excitation thanks to increases in hole density and band turning in composites. Meanwhile, the low-work function in the BST matrix establishes an interface potential with a height of 2.03 eV that efficiently filters low energy carriers, and consequently alleviates the decrement of Seebeck coefficients. Upon LVO addition, not only does the bipolar thermal conductivity decrease but the lattice thermal conductivity approaches the amorphous limit due to enhanced phonon scattering mechanisms at incoherent interfaces. A significant thermoelectric figure of merit, ZT of 1.26 and ZT avg = 1.13 are achieved for the sample with 5 wt% of LVO in BST, which is about 26% and 20% higher than the pristine BST, respectively, thanks to its optimized power factor and low thermal conductivity. Additionally, LVO dispersion strengthens the mechanical properties of the composites, demonstrated in their enhanced hardness and compressive strength. [ABSTRACT FROM AUTHOR]

High-quality SnS nanosheets with uniform sizes were prepared by a facile wet-chemical synthesis. The electrical properties of the SnS samples were optimized by enhancing the hole concentration from 3.2×1018 cm−3 to 4.8×1019 cm−3 via introducing Sn vacancies, adding SnSe, and embedding Ag atoms, and the peak PF increased to 0.48 × 10-3 W⋅m-1K−2 after Se and Ag co-doping. Correspondingly, the lattice thermal conductivities decreased from 0.8 W⋅m-1K−1 to 0.47 W⋅m-1K−1 due to enhanced phonon scattering. A remarkable zT value of about 0.80 at 873 K was obtained in the Se and Ag co-doped sample, which provides a novel method to prepare high-quality and high-performance thermoelectric semiconductors via a wet chemical synthesis. [Display omitted] • Uniform and well-dispersed SnS nanosheets were prepared by a wet chemical synthesis. • Carrier concentration was enhanced via element doping and combined effects. • The PF increased from 0.15 × 10-3 to 0.48 × 10-3 W m-1K−2 after Se and Ag co-doping. • A high zT value of about 0.80 at 873 K was obtained in the Se and Ag co-doped sample. Tin sulfide (SnS) is a low-cost, earth-abundant, and eco-friendly thermoelectric (TE) material whose layered orthorhombic structure is similar to that of SnSe; however, current studies on SnS are limited because of its difficult synthesis due to the use of volatile sulfur, and its thermoelectric figure of merit (zT) is also low because of its intrinsically low electrical conductivity. Herein, we present a facile wet chemical synthesis to prepare uniform and well-dispersed SnS nanosheet crystals. Low-rate initial production with 3.5 L solvent was performed to obtain high-quality crystals, and also to adapt the process to commercial preparation. The carrier concentrations were enhanced from 3.2 × 1018 cm−3 to 4.8 × 1019 cm−3 (at 873 K) step-by-step via increasing Sn vacancies, adding SnSe, and embedding Ag atoms. The maximum power factor (PF) at 873 K of 0.48 × 10−3 W⋅m−1K−2 was achieved in the selenium-silver co-doped sample, which presented a state-of-the-art value for the polycrystalline SnS. Correspondingly, the lattice thermal conductivities (κ L) decreased from 0.8 W⋅m−1K−1 to 0.47 W⋅m−1K−1 (at 873 K) due to enhanced phonon scattering. The highest zT was 0.80 at 873 K, which is about 5 or 6 times higher than those of the pristine SnS(1:1) or SnS(1:0.8) samples. These findings provide a novel method to prepare high-quality and high-performance TE semiconductors via a wet chemical synthesis. [ABSTRACT FROM AUTHOR]

• Increased electrical conductivity of ~97% via zero-barrier charge injection. • Enhanced Seebeck of 553 μV K−1 due to the modified band level by hole injection. • Reduced thermal conductivity to ~44% by all-scale hierarchical phonon scattering. • Achieved high zT = 1.18 for optimized MoS 2 /MoO 3 interface via simple chemical route. As a consequence of high thermoelectric (TE) properties, low cost, and environmental friendliness, molybdenum disulphide (MoS 2) has emerged as the material of choice for TE generator for room temperature to mid temperature (800 K) applications. The compound has high figure-of-merit (zT) value due to the combination of anharmonicity, valley degeneracy and ultralow thermal conductivity (at low-dimension). In this work, MoS 2 /MoO 3 hierarchical structures are prepared by hydrothermal method and it exhibits improved TE performance. The enhanced phonon scattering is observed in thin layered nanosheets and improved electrical conductivity by zero-barrier charge injection at MoS 2 /MoO 3 interface. While MoO 3 supports in optimizing the electrical transport properties, low-dimension layered MoS 2 nanosheets and interfaces of MoS 2 /MoO 3 results in phonon scattering. High resolution transmission electron microscopy (HRTEM) indicates enriched interface of nanocrystals and nanosheets. This results in ~97% increased electrical conductivity compared to the pristine MoS 2 at 600 K while retaining ~44% reduction in thermal conductivity at 550 K. More importantly, the phonon scattering and carrier optimization have been tailored strategically, and a relatively high power factor (PF) of 411.43 µW m−1 K−2 at 600 K with a significantly lowered thermal conductivity of 0.16 W m−1 K−1 at 550 K have been achieved. The maximum zT of 1.18 at 600 K is achieved for hierarchical MoS 2 nanosheets/MoO 3 nanocrystal's optimized effective interface. [ABSTRACT FROM AUTHOR]

• Achieving texture-degree-control to control the thermoelectric performance of layered-structured materials. • Proposing that the texture degree of Bi 2 Te 3 -based materials should be properly designed. • Linking nanostructure engineering with texture engineering to manipulate the thermoelectric properties. In this study, Bi 2 Te 3 nanostructures were synthesized with controlled morphologies by using a solvothermal process and then sintered by spark plasma sintering to obtain bulk samples with controllable texture degrees. The sintered nanostructured Bi 2 Te 3 pellets show texture-dependent thermoelectric properties, in which their Seebeck coefficient, electrical conductivity and thermal conductivity can be optimized by the proper texture design to simultaneously secure a high carrier mobility and strong phonon scattering, resulting in a peak ZT value of ~0.69 at 333 K. This study reveals the potential of texture engineering in developing high performance anisotropic thermoelectric materials. [ABSTRACT FROM AUTHOR]