The widespread application of thermoelectric (TE) technology demands high‐performance materials, which has stimulated unceasing efforts devoted to the performance enhancement of Bi2Te3‐based commercialized thermoelectric materials. This study highlights the importance of the synthesis process for high‐performance achievement and demonstrates that the enhancement of the thermoelectric performance of (Bi,Sb)2Te3 can be achieved by applying cyclic spark plasma sintering to BixSb2–xTe3‐Te above its eutectic temperature. This facile process results in a unique microstructure characterized by the growth of grains and plentiful nanostructures. The enlarged grains lead to high charge carrier mobility that boosts the power factor. The abundant dislocations originating from the plastic deformation during cyclic liquid phase sintering and the pinning effect by the Sb‐rich nano‐precipitates result in low lattice thermal conductivity. Therefore, a high ZT value of over 1.46 is achieved, which is 50% higher than conventionally spark‐plasma‐sintered (Bi,Sb)2Te3. The proposed cyclic spark plasma liquid phase sintering process for TE performance enhancement is validated by the representative (Bi,Sb)2Te3 thermoelectric alloy and is applicable for other telluride‐based materials.

Bi2Te3 thermoelectric materials are utilized for refrigeration for decades, while their application of energy harvesting requires stable thermoelectric and mechanical performances at elevated temperatures. This work reveals that a steady zT of ≈0.85 at 200 to 300 °C can be achieved by doping small amounts of copper iodide (CuI) in Bi2Te2.2Se0.8–silicon carbide (SiC) composites, where SiC nanodispersion enhances the flexural strength. It is found that CuI plays two important roles with atomic Cu/I dopants and CuI precipitates. The Cu/I dopants show a self‐tuning behavior due to increasing solubility with increasing temperatures. The increased doping concentration increases electrical conductivity at high temperatures and effectively suppresses the intrinsic excitation. In addition, a large reduction of lattice thermal conductivity is achieved due to the “in situ” CuI nanoprecipitates acting as phonon‐scattering centers. Over 60% reduction of bipolar thermal conductivity is achieved, raising the maximum useful temperature of Bi2Te3 for substantially higher efficiency. For module applications, the reported materials are suitable for segmentation with a conventional ingot. This leads to high device ZT values of ≈0.9–1.0 and high efficiency up to 9.2% from 300 to 573 K, which can be of great significance for power generation from waste heat.

Lead-free manganese telluride has been considered to be a promising candidate for mid-temperature thermoelectric materials. In this work, we report point defect scattering-induced reduction of thermal conductivity in MnTe with Se alloying, fabricated by a facile method combining mechanical alloying and spark plasma sintering. A low lattice thermal conductivity of 0.56 W/mK was obtained for MnTe0.92Se0.08, which is quite close to the amorphous limits. A detailed Debye model analysis reveals the underlying mechanism of phonon scattering and well predicts the thermal conductivity with different contents of Se. Meanwhile, a slight increase of carrier concentration was also observed after Se alloying, accompanied by a variation of energy gap that may be associated with the competition among anions in trapping charges. Further Na doping leads to enhanced electrical transport properties, achieving a maximum ZT value of 1.03 at 873 K. An average ZT of 0.52 and a calculated efficiency of more than 9% also suggest the promising application of MnTe at medium temperatures.

With the aim to improve the controlling efficiency of engineering project, this essay probes into the comprehensive evaluation of controlling efficiency of engineering project and put forward scientific comprehensive evaluation method to provide support to reasonable comprehensive evaluation of controlling efficiency of engineering project. Complete comprehensive evaluation index system of controlling efficiency of engineering project is constructed from three aspects, i.e. implementation efficiency of construction objective, external coordination efficiency and professional qualification enhancement efficiency; based on matter-element analytical method, mathematic model that could evaluate controlling efficiency of engineering project comprehensively is constructed.

This study is aimed at obtaining (K,Na)NbO3 powders with wide grain size distribution methods. (K,Na)NbO3 powders were successfully synthesized by different ways, including hydrothermal method, sol-gel method, and molten-salt method. The experiment results showed that the hydrothermal and sol-gel methods could not control the grain size of the (K,Na)NbO3 powders effectively . The grain size of (K,Na)NbO3 powders can be only tailored by the molten-salt method through controlling the starting oxide powder morphology, as well as crystallization temperature. The grain size was not affected by the experimental parameters whether or not the initial powders were milled. Furthermore, it has been found that the crystallization temperature could change the grain size of the powders monotonously. The (K,Na)NbO3 powders synthesized by molten salt method distributed from nanoscale to micron level, which can lay the foundation for further research on the grain size effect of (K,Na)NbO3 lead free piezoelectric ceramics.