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With the fast evolution in greenhouse gas (GHG) emissions (e.g., CO2, N2O) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public health, and the environment. To reduce GHG emissions, besides minimizing waste heat production at the source, an integrated approach should be adopted for waste heat management, namely, waste heat collection and recycling. One solution to enable waste heat capture and conversion into useful energy forms (e.g., electricity) is employing solid-state energy converters, such as thermoelectric generators (TEGs). The simplicity of thermoelectric generators enables them to be applied in various industries, specifically those that generate heat as the primary waste product at a temperature of several hundred degrees. Nevertheless, thermoelectric generators can be used over a broad range of temperatures for various applications; for example, at low temperatures for human body heat harvesting, at mid-temperature for automobile exhaust recovery systems, and at high temperatures for cement industries, concentrated solar heat exchangers, or NASA exploration rovers. We present the trends in the development of thermoelectric devices used for thermal management and waste heat recovery. In addition, a brief account is presented on the scientific development of TE materials with the various approaches implemented to improve the conversion efficiency of thermoelectric compounds through manipulation of Figure of Merit, a unitless factor indicative of TE conversion efficiency. Finally, as a case study, work on waste heat recovery from rotary cement kiln reactors is evaluated and discussed. 

Hypothetical half-Heusler (HH) ternary alloy of CoVSn has already been computationally investigated for possible spintronics and thermoelectric applications. We report the experimental realization of this compound and the characterizations of its thermoelectric properties. The material was synthesized by a solid-state reaction of the stoichiometric amounts of the elements via powder metallurgy (30 h mechanical milling and annealing at 900 °C for 20 h) and spark plasma sintering (SPS). The temperature-dependent ternary thermodynamic phase diagram of Co-V-Sn was further calculated. The phase diagram and detailed analysis of the synthesized material revealed the formation of the non-stoichiometry HH CoVSn, mixed with the binary intermetallic phases of SnV3, Co2Sn, and Co3V. The combination of X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermoelectric transport properties confirmed the formation of a multi-phase compound. The analysis revealed the predicted thermoelectric features (zT = 0.53) of the highly doped CoVSn to be compromised by the formation of intermetallic phases (zT ≈ 0.007) during synthesis. The additional phases changed the properties from p- to overall n-type thermoelectric characteristics. 

Mechanical and thermal stability are the two challenging aspects of thermoelectric compounds and modules. Microcrack formation during material synthesis and mechanical failure under thermo‐mechanical loading is commonly observed in thermoelectric materials made from brittle semiconductors. Herein, the results of graphene‐nanoplates (GNPs) reinforcement on the mechanical and thermoelectric properties of MnTe compound are reported. The binary antiferromagnetic MnTe shown promising thermoelectric characteristics due to the paramagnon–hole drag above the Néel temperature. In this study, different bulk MnTe samples are synthesized with the addition of GNPs in a small quantity (0.25–1 wt%) by powder metallurgy and spark plasma sintering. The thermoelectric factors, magnetic behavior, microstructure, and mechanical properties of the samples are evaluated and analyzed. Nearly 33% improvement is observed in the fracture toughness of MnTe reinforced with 0.25 wt% GNPs compared to the pristine structure. The Néel temperature remains approximately unaffected with the GNP inclusion; however, the low‐temperature ferromagnetic phase impurity is significantly suppressed. The thermal conductivity and power factor decrease almost equally by ≈34% at 600 K; hence, the thermoelectric figure‐of‐merit is not affected by GNP reinforcement in the optimized sample.