We report a melt spinning technique followed by a quick spark plasma sintering procedure to fabricate high-performance $p$ -type ${\text{Bi}}_{0.52}{\text{Sb}}_{1.48}{\text{Te}}_3$ bulk material with unique microstructures. The microstructures consist of nanocrystalline domains embedded in amorphous matrix and 5–15 nm nanocrystals with coherent grain boundary. The significantly reduced thermal conductivity leads to a state-of-the-art dimensionless figure of merit $ZT\sim 1.56$ at 300 K, more than 50% improvement of that of the commercial ${\text{Bi}}_2{\text{Te}}_3$ ingot materials.

Half-Heusler (HH) alloys have attracted considerable interest as promising thermoelectric (TE) materials in the temperature range around 700 K and above, which is close to the temperature range of most industrial waste heat sources. The past few years have seen nanostructuing play an important role in significantly enhancing the TE performance of several HH alloys. In this article, we briefly review the recent progress and advances in these HH nanocomposites. We begin by presenting the structure of HH alloys and the different strategies that have been utilized for improving the TE properties of HH alloys. Next, we review the details of HH nanocomposites as obtained by different techniques. Finally, the review closes by highlighting several promising strategies for further research directions in these very promising TE materials.

High performance ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ bulk materials with layered nanostructure have been prepared by combining melt spinning technique with spark plasma sintering, and their thermoelectric transport properties are investigated. The electrical conductivity increases greatly and the lattice thermal conductivity decreases significantly with the increase of the roller’s linear speed. These lead to a great improvement in the thermoelectric figure of merit $\left(ZT\right)$ . The maximum $ZT$ value of 1.35 is obtained at $300\mathrm{K}$ for the sample which is prepared by melt spinning with roller linear speed of $40\mathrm{m}∕\mathrm{s}$ . Compared with the zone melting sample, it increases by 73% at the same temperature.

We report a detailed description of an innovative route of a melt spinning (MS) technique combined with a subsequent spark plasma sintering process in order to obtain high performance $p$ -type ${\text{Bi}}_{0.52}{\text{Sb}}_{1.48}{\text{Te}}_3$ bulk material, which possesses a unique low-dimensional structure. The unique structure consists of an amorphous structure, 5–15 nm fine nanocrystalline regions, and coherent interfaces between the resulting nanocrystalline regions. Measurements of the thermopower, electrical conductivity, and thermal conductivity have been performed over a range of temperature of 300–400 K. We found that MS technique can give us considerable control over the resulting nanostructure with good thermal stability during the temperature range of 300–400 K and this unique structure can effectively adjust the transport of phonons and electrons, in a manner such that it is beneficial to the overall thermoelectric performance of the material, primarily a reduction in the lattice thermal conductivity. Subsequently, this results in a maximum figure of merit $ZT$ value of 1.56 at 300 K for $p$ -type ${\text{Bi}}_{0.52}{\text{Sb}}_{1.48}{\text{Te}}_3$ bulk material. This $ZT$ value is over a 50% improvement of that of the state of the art commercial ${\text{Bi}}_2{\text{Te}}_3$ materials. We also report results of thermal cycling of this material for over one hundred cycles between 300–400 K. Our work offers an innovative route for developing high performance bismuth telluride based alloys and devices, which have even broader prospects for commercial applications. This technique may also be applicable to other thermoelectric materials.

The abundance of low-temperature waste heat necessitates the development of reliable and scalable thermal-to-electric energy conversion technology. The thermoelectric device is one viable option. Commercially available Bi₂Te₃-based materials are optimized for near room temperature cooling applications. Currently there are no mass-produced materials available for 400 K to 650 K thermoelectric power generation. We report the successful realization of high performance n-type Bi₂(Te_1−xSe_x)₃-based materials for the temperature range of interest, using a commercial zone-melting technique. The introduction of Se effectively increases the band gap, which significantly suppresses the “turn-over” in Seebeck coefficient and the appearance of a pronounced bipolar effect, shifting the corresponding temperature of the optimum thermoelectric figure of merit ZT towards a higher temperature range. Furthermore, we demonstrate that the electron concentration of Bi₂(Te_0.5Se_0.5)₃ can be effectively adjusted by iodine doping. The samples with electron concentrations between 3 × 10¹⁹ and 4.5 × 10¹⁹ cm⁻³ display optimal thermoelectric performances. The highest ZT value reaches 0.86 at 600 K for the sample with the electron concentration of 4.0 × 10¹⁹ cm⁻³, whose average ZT between 400 K and 640 K is 0.8, making this scalable zone-melted low-Te content Bi₂(Te_0.5Se_0.5)₃ compound a promising candidate for low-temperature power generation.