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Fe3Al2Si3-based thermoelectric materials have low production costs and are environmentally friendly. However, they are usually synthesized via arc-melting, resulting in poor compositional accuracy. Here, Fe36.5Al23.5 + xSi40−x (x = 1.7, 1.8, 1.9, 2.0, and 2.1) compounds with low thermal conductivity (κ) were prepared via levitation melting. The x = 2.1 composition may be the threshold for a p-to-n-type transformation. A minimum κ of ~3.17 W/mK was obtained in Fe36.5Al25.4Si38.1 at 323 K, a decrease of 42.3% relative to the parent Fe3Al2Si3 compound. Moreover, the largest maximum power factor of ~461 μW m−1 K−2 was obtained in Fe36.5Al25.4Si38.1 at 373 K. Using composition self-tuning, a peak figure of merit of ~0.055 was obtained in Fe36.5Al25.4Si38.1 at 423 K. This approach for realizing low κ and a high compositional accuracy should impact the development of advanced room-temperature thermoelectric materials with narrow bandgaps. [ABSTRACT FROM AUTHOR]

Half-Heusler alloys (HHs) as medium- and high-temperature thermoelectric materials have attracted increasing considerable attention, owing to their excellent mechanical properties and thermal stability. Nonetheless, the intercoupling between the Seebeck coefficient and electrical conductivity, and their high thermal conductivity limit the furthermore enhancement of their thermoelectric properties. This review systemically summarizes and analyses the various current strategies for improving thermoelectric properties, such as manipulating band structure, optimizing electron and phonon transports, and constructing high configurational entropy, etc. Moreover, the possible deficiencies of the existing electric-phonon transport mechanisms are highlighted and discussed, which aiming to provide a meaningful guide for future efforts to accelerate the development of HHs. Finally, based on current research, a new potential future for the integration of single crystal technology and high-entropy effect is introduced for HHs. [ABSTRACT FROM AUTHOR]